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WELDING 



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WELDING 

THEORY, PRACTICE, 
APPARATUS AND TESTS 

ELECTRIC, THERMIT 
AND HOT-FLAME PROCESSES 



BY 

RICHARD N. HART, B. S. 



McGRAW-HILL BOOK COMPANY 

239 WEST 39TH STREET, NEW YORK 

6 BOUVERIE STREET, LONDON, E. C. 

1910 



T*' 



<'^> 



Copyright, 1910 

BY THE 

McGraw-Hill Book Company 



Printed and Eleclrotyped by 

The Maple Press 

York, Pa 



€CI.A:^;o.s7S 



r 



PREFACE 



In spite of the numerous data on the theory, practice, appara- 
tus, and tests of welding contained in the trade journals and 
metallurgical books, no previous attempt has been made to present 
this data in sequence under one cover. But in the last fifteen 
years the subject has begun to be of interest and importance. The 
electric, thermit, and hot-flame processes are welding all of the 
metals and are doing repeat and repair work that has never before 
been attempted. New brazing methods have also been success- 
fully tried out and the range of good solders greatly increased. 

I have given separate chapters to the commercial metals. 
Few of the metallurgies give much space to the working proper- 
ties of the metals, especially the welding property, which is often 
merely mentioned. 

Test and cost data must be taken with a grain of salt. The 
test data have been compiled from various sources. Those tests 
given for iron are standard and cannot be questioned. Those 
tests given for the special processes are more recent and in most 
cases have been made by interested parties. They are no doubt 
accurate, but at present the special processes cannot be so well 
represented by test data, as by the actual work they turn out. 
The same may be said of cost data. The prospective purchaser 
of welding machinery must figure the cost of his apparatus plus 
the cost of labor and the depreciation. But above all, he must 
satisfy himself that the apparatus he chooses is the best for his 
kind of welding. 

I wish to express my thanks for assistance received from the 
different welding companies mentioned herein; also to James 
H. DeLong, for special analyses; Dr. Edward Hart, Dr. Joseph 
W. Richards, Prof. Oliver P. Watts, Otis Allen Kenyon, E. A. 
Colby, of Baker & Co., and to many others. 

R. N. Hart. 

Los Angeles, Cal., October, 1910. 

V 



CONTENTS 



PAGE 

Preface . . , v 

Definitions and introduction xi 

Theories of welding xiv 

The Metals 

Iron I 

Malleable ron ... i 

How to weld iron 2 

Points in practice 3 

Welding fires 4 

Causes of poor welds 6 ■ 

Effect of impurities 8 

Tests of smith welds 12 

Conclusions 15 

Platinum — Descriptive and historical — Welding, including irid- 
ium and osmium 15 

Gold — Descriptive — Welding and soldering 18 

SUver — Descriptive — Welding and soldering 19 

Aluminium — Descriptive — Solders — Welding processes — Con- 
clusion 20 

Copper — Descriptive — Welding 25 

Nickel — Descriptive — Welding 27 

Welded products 28 

Wrought-iron pipe 29 

Chain making 29 

Miscellaneous 30 

Electric Welding 

General 33 

The La Grange-Hoho process 34 

The Zerener electric blowpipe 34 

vii 



Vlll CONTENTS 



PAGE 



The Bernardos arc-welding process 35 

Apparatus and current: Generator — Table, switches, controll- 
ing apparatus, carbon — Workman's protective apparatus 38 

Practice 40 

Cutting metals with electric arc 41 

The Thomson process 42 

Apparatus and current: Generator — Transformer — Regulat- 
ing apparatus — Clamps 43 

Practice 54 

Adaptability — Locomotive flue-welder 59 

Rail welding 66 

Electric resistance heater 69 

Tests 70 

Hot-flame Welding 

The Oxy-acetylene process 73 

General 73 

Apparatus and gases: The torch — Electrolysis of water — 
Storage oxygen — Oxygenite — Oxygen from chlorate — Acet- 
ylene — The acetylene generator — Dissolved acetylene . . 75 

Practice — The flame 96 

How to weld 97 

Adaptability loi 

Typical welds and repairs: Repairing cracks, steamer "Eugene 
Periere" of the French Line — Repairing corroded plates 

plates on the "Cholon." 102 

Acetylene welding versus riveting 106 

Repairing defective castings 108 

How to cut metals 109 

Costs 112 

Chemistry and thermics 113 

Testing 115 

The Oxy-hydrogen process 115 

General 115 

Apparatus — The flame 116 

Thermit 

The Thermit process 121 

. General — History 121 

Apparatus and rail welding — Crucible — ISIold 123 



CONTENTS ix 

PAGE 

Practice — Setting the pieces — Cleaning the pieces — Preheat- 
ing — Safe-guarding the mold — Amount of thermit — The 
reaction — After pouring — Nickel addition — Titanium addi- 
tion 131 

Butt-welding of pipes 137 

Mending defective castings 141 

Thermit in foundry practice — ^Poling — Adaptability .... 142 
Typical welds — ^Repair of the "Betsy Ann" — Repair of the 

steamship "Corunna" — Weld on electric motor shaft . 146 

Chemistry and thermics — ^Heat of reaction 152 

Testing — Tests Nos. 1-6 155 

The Lafitte welding plate 158 

The Ferrofix brazing process . 160 

Brazing and soldering 165 

Glossary of terms ........o»....,.o...i75 



DEFINITIONS AND INTRODUCTION 



According to the Standard Dictionary, to weld is to "unite, 
as heated metal, in one piece or mass under the hammer or by 
pressure." 

The Century Dictionary says, "To unite or consoHdate, as 
pieces of metal or metallic powder, by hammering or compres- 
sion, with or without previous softening by heat." * * * "term 
is more generally used when the junction of the pieces is effected 
without the actual fusing point of the metal having been reached." 
While the Standard adds, " Metals are weldable in proportion to 
the length of time they will stay under heat in a plastic condition 
without melting." 

Welding is distinguished from soldering, which is, according to 
the Standard, "To unite, as two metallic substances, by solder." 
The Century, "To unite by a metallic cement." * * * "Every 
kind must be used as its own melting point, which must be al- 
ways lower than that of the metals to be united." 

I give these definitions because there is some confusion of the 
terms; and naturally so, as the two processes often are undistin- 
guishable. Thus two unlike metals, as iron and platinum, may be 
welded; while a fractured steel bar may be united by placing 
platinum foil between the pieces, pressing strongly together and 
heating moderately. This is strictly welding, yet the platinum 
foil is solder. In the recent processes of welding by fusion, the 
molten metal becomes a solder. Brazing is classed as soldering, 
but when brass is brazed the process is as nearly welding as the 
so-called autogenous weld. 

The word autogenous is misapplied to welding. It means 
self- produced. The melted weld of the oxy-hydrogen or acetylene 
flame is a soldering process in which the metal produces its own 
solder. However, it makes a catchy trade-name. 

Welding, under different names, is a property possessed by 
many substances, both elemental and compound. According to 

xi 



Xll WELDING 

Roberts- Austen/ who devotes considerable space to the flowing 
property of metals, "' welding is the property possessed by metals, 
which on cooling from the molten state pass through a plastic 
stage before becoming perfectly solid, of being joined together by 
the cohesion of the molecules that is induced by the application of 
an extraneous force, such as hammering." 

In general, welding occurs if cohesion between the molecules of 
the two pieces can be induced. This cohesion may amount to 
diffusion when the two pieces are of unlike substance, and the 
metal at the weld will be found to be an alloy of the two, Thus 
gold and lead, pressed together for several weeks, will weld at 
ordinary temperature. At loo deg. C. they will weld in less 
time, and the weld will be an alloy of gold and lead. 

Welding and diffusion are not inseparable, however. For the 
welding by diffusion of lead and gold is weaker than the first- 
named cold weld. While the diffusion of mercury through an- 
other metal invariably produces weakness of that metal, some- 
times disintegration. 

Regelation is the name given to the welding of two pieces of 
ice. Faraday is credited with this discovery. He found that 
two pieces of ice slightly below freezing point, if pressed together 
will weld. Wrightson" states that both iron and ice suffer a 
drop in temperature when pressed together. He heated two 
irons to the plastic state in an electric welder and pressed them 
together. The recording pyrometer showed a sudden fall of 
from 19 deg. to 57 deg. C. He further states that iron in- 
creased almost 7 per cent, in volume on becoming plastic, and 
tries to trace an analogy between the behavior of iron and ice. 
It has since been found that regelation is a property possessed 
in some degree by most crystalline substances. Pure crystalline 
salts will regelate under pressure at moderate temperature. Even 
such a substance as bismuth will regelate. 

Evidently welding depends upon two things: 

I. The flow. 

Most of the so-called solids are fluid to some extent. Highly 
crystalline, refractory rocks will flow under great pressure. The 

' "Introduction to Metallurgy," p. 47. 

^ Jaurnal of the Iron and Steel Institute, 1895, Vol. I, p. 499. 



DEFINITIONS AND INTRODUCTION xiil 

walls of some deep mines have flowed together in the course of 
time. A rod of glass or of sealing-wax will bend or flow if it 
supports a weight for several days. Lead, sodium, etc., flow 
readily under pressure. 

Flow is almost synonymous with malleability, the difference 
being a matter of time. Many substances which flow slowly wfll 
not withstand the shock of the hammer. 

Most metals flow at all temperatures from normal to melting 
point, but they are the most easily weldable within the range of 
greatest plasticity. But their Vv^elding also depends upon — 

2. The wetting or cohesion of the two substances. 

Two pieces of the same or different substance will not weld if 
their surfaces do not cohere, no matter how malleable or fluid 
they may be. Aluminum is a notable instance. The metal is 
quite malleable at most temperatures, but a microscopic film of 
oxid prevents the two surfaces from wetting one another. Iron in 
a lesser degree is troubled with a coating of oxid at welding tem- 
perature. Any flux which will clean off both surfaces will allow 
a weld to be made. In proportion to the ease with which one can 
have and hold a clean surface of the metals in the range of plas- 
ticity, in that proportion will welding be feasible. The welding 
of malleable metals is dependent on the behavior of the oxids 
which form on their surface. In proof of this is the remarkable 
experiment of Chernoff^ in 1877. He showed that a partial weld 
of two pieces of iron could be made at the low temperature of 650 
deg. C, which is at least 700 deg. below common welding heat. 
The two surfaces were planed and highly polished. Pressure was 
applied for several days, when it was found that there was a 
partial weld. This is similar to the well-known experiment in 
physics where two plane and highly polished surfaces of glass 
are pressed together. The surfaces will cohere to some extent. 

These two experiments seem to show that whatever assists 
cohesion, assists the welding. There are numerous instances of 
welding among non-metallic substances which do not oxidize 
at the welding heat. Glass is too well-known to need explana- 
tion. Pieces of horn can be joined under pressure of hot plates 
if the horn be kept moist. 

^ Revue Universalle des Mines, Vol. I, 1877, p. 411. 



XIV WELDING 

Metals newly nascent, in a fine powder, can be welded into a 
solid piece by a stroke of the hammer. Apparently for the reason 
that the grains of powder have bright, clean faces. Most of the 
malleable metals are so weldable. 

THEORIES OF WELDING 

In 1877, Holley^ advanced the theory that irons weld in pro- 
portion to their mobility or flowing, and inversely as oxidation 
of the welding surfaces occurs. He thought that the more 
plastic or more nearly melting point the irons were, the more 
readily they would weld. But with every increase in heat was a 
corresponding readiness to oxidize — especially on the part of 
carbon and iron. This oxid interposed a mechanical difficulty 
to perfect welding. 

This theory does not satisfy Campbell" who insists that im- 
purities tend to crystallization in the body of the iron. Carbon, 
which is the principal offender, and sulphur, phosphorus, and 
other ingredients, all form alloys or compounds with the pure fer- 
rite. Ferrite itself is exceedingly malleable and mobile. But a 
mixture of ferrite and several of the carbon compounds, as cemen- 
tite, martensite, etc., is stiff above red heat in proportion to the car- 
bon present. Campbell thinks that such a steel, which is really a 
mineral with a granitic structure, will not weld, because it refuses 
to flow. He claims that oxidation troubles are actually less, 
because the chemical combination of the iron oxid with the 
impurities and their oxids would give a self-fluxing surface. 

According to Campbell, then, those impurities which caused 
decided crystallization with accompanying brittleness, interfered 
with the flow at high heat and prevented welding. Manganese, 
it is true, makes a more brittle iron, up to 1.20 per cent; but 
it prevents crystallization of sulphur, etc., and is an aid in welding. 

For ordinary and commercial purposes the welding must be 
done in a few seconds' time, and the previous cleaning and heating 
must not take long. This at once limits to a very few the num- 
ber of metals which can be welded; were it not for the recent 

' Trans. American Institute of Mining Engineers, Vol. VI, p. 112. 
^ "Metallurgy of Iron and Steel," p. 589. 



THEORIES OF WELDING XV 

remarkable advance due to the electric, oxy-hydrogen and acety- 
lene processes of melting, welding would be confined to iron, plat- 
inum, nickel, and gold. Other metals would be joined by solder- 
ing and brazing, and even then the metal worker would have great 
difficulties with aluminum and many alloys. 

I will first take up iron and steel welding. As much research 
work has been done on the metallurgy of iron as on all of the other 
metals combined. It is extremely probable that many of the 
difficulties and problems arising from proportions of impurities 
and methods of producing will apply equally to other metals. 
For this reason, and because of its overwhelming importance, I 
will treat of iron more thoroughly. 



WELDING 



Part I— The Metals 

IRON 

Pure or nearly pure iron is readily weldable at a white heat. 
Malleable, or nearly pure wrought iron, is known as weld iron. 
The range of temperature in which it can be welded is very 
wide: it runs from the imperfect weld at cherry- red, to dazzling 
white, when the welding property is lost just before the iron 
melts. According to Pouillet, the different colors of heated 
metals are represented approximately by the temperatures given: 

Deg. C 

Incipient red 525 

Dark red : 700 

Incipient cherry 800 

Clear cherry-red 1000 

White 1300 

Dazzling white 1500 

Melting 155° 

Wrightson ' states that he found iron to increase in volume as 
much as 7 per cent, when passing into the plastic stage. 

Malleable Iron. — Weld iron is a name occasionally used to 
describe malleable iron, indicating that it is pure enough to be 
welded. Malleable iron is produced by the puddling process. 
It is made by melting up pig iron and scrap in an open-hearth 
furnace and burning out the greater part of the silicon, man- 
ganese, and carbon in the order named. As the burning continues 
the melting point of the iron rises, and it becomes a pasty mass 
permeated with slag from the stirring. This nearly pure iron 
is gathered into "puddle balls," and taken to the rolls at a white 
heat. It is rolled or hammered out into long strips, the strips 
are cut, reheated to white heat, and welded together between the 
rolls or beneath the hammer. To produce the finest wrought 

' Journal of the Iron and Steel Institute, 1895, ^^o'- I- P- 4^3- 

I 




2 WELDING 

iron, the process of rolling and welding is repeated. This is 
the puddling process in brief; its object is to squeeze and work 
the slag out of the iron and to give the iron a fibrous structure 
like rolled copper. 

The principal chemical difference between wrought iron and 
steel is the carbon content. In fact, except for its high carbon, 
basic open-hearth steel is purer than most malleable irons. 

All weldable iron is not malleable, but it is weldable in pro- 
portion to its malleability. 
As is seen in the foregoing 
process, the iron is welded 

several times. 

Fig. I. — ^\'iews of scarfed bars for tt j.^ iir^u t*^». 

lap welding. HoW tO Wcld IrOIl.— 

The mechanics of a 
"smithed" weld is in the main as follows: Suppose the smith 
wishes to join two short bars of malleable iron, of cross-section 
I by 2 inches. He first hammers or cuts a convex bevel or 
"scarf" on the ends of each bar, as shown in Fig. i. 

The heating must be done in a coke or coal forge. Coke is 
the best fuel for the reason that it gives a good reducing flame. 
The fire is blown with the bellows until it is at a high heat. The 
ends of the bars are thrust well into the midst of the ignited 
coke and more coke is piled over them. The blowing is con- 
tinued until the bars are red-hot on the ends, when the smith 
takes them out with pliers and dips them into pure sand or borax 
near by. This is the flux, and 
it so acts on the surface of the 



iron as to clean it of rust and y, ^ 

forms a glass that protects ^ t, • . . . , , ,. 

, ^ Fig. 2. — Bars in position for lap welding. 

the fresh iron from further 

rust. The smith puts his irons back into the forge again and 

heats them until white. 

When white, or nearly white-hot, the smith takes one bar in 
his pliers, his helper takes the other, and they place them together 
on the anvil, the one lapping the other (Fig. 2). Both the smith 
and his helper give the pieces quick, light blows with their 
hammers until the plastic iron is well-joined. They turn the 
irons while hammering to get an even weld on all sides. 



IRON 3 

The smith will try to weld at a white, but not a dazzling white, 
heat, and he will try to complete it without putting it back into 
the fire for a reheating. 

When the weld is finished, he may give it a special shape by 
placing it between swage blocks and hammering. 

This simple operation of welding requires much skill, as will 
appear. The smith may find that with all his skill his joint is 
bad or that his iron will not join at all. 

Points in Practice. — In practice there are the usual number 
of details requiring skill that the smith must observe. 

The contact faces should always be shaped so that their 
middle points touch first and so that hammering causes union 
first at the middle. This prevents slag becoming enclosed. 

The heating should be done rather slowly, so that the pieces 
will be of uniform heat at the weld. Both irons should be of the 
same temperature. To effect this the smith must not blow up 
his fire too hot and must watch the color of both irons. A deep 
bed of coals will give a flame the least oxidizing, because most of 
the oxygen will burn to carbon monoxid or dioxid. 

The welding heat is quite different for different irons. The 
smith must use his judgment, taking good care he does not over- 
heat his irons. Overheated iron, miscalled "burnt iron," will 
be brittle on cooling. Steel is much more sensitive to overheat- 
ing than iron. It is seldom safe to heat steel above redness. 

The iron should be well fluxed directly on the contact surfaces, 
and not merely around them, as is too often the case. The com- 
mon fluxes for iron are pure silica (river sand) and borax. Im- 
pure malleable irons are self-fluxing to a certain degree, but this 
cannot be relied on. Other fluxes are calcined borax and sal 
ammoniac. One writer^ recommends powdered marble, which 
is limestone, the flux of the blast furnace. Borax is recommended 
for steel on steel or steel on iron, as silica is inadequate.^ Besides 
fluxing the bars before raising them to welding heat, the smith 
may sprinkle calcined borax on the irons when they are ready to 
weld, to replace it on surfaces accidentally rubbed bare in the 
forge. 

' "The Blacksmith's Guide," J. S. Sallows. 

^ "Testing of Materials of Construction," W. C. Unwin, 1899, p. 292. 



4 WELDING 

The hammering, or "working," is very important, and must 
be done rapidly. The smith manipulates his bars so that welding 
begins at a middle point and works outward, driving the slag 
away from it. The first few blows of the hammer should not be 
heavy. If the pieces are large or the smith slow, his heat will 
fall before the weld is finished and he must put his bars back in the 
fire. Second heating must be avoided if possible; slag is apt to 



Fig. 3. — Lap weld. No upset. Fig. 4. — Lap weld. Upset. 

get in the weld or the pieces may become " burnt," to say nothing 
of the time lost. 

The different kinds of welds known to the smith — ^butt, lap, 
scarf, jump, cleft — are variations of simple welds. Illustrations 
of them and of how the stock should be shaped are given in fig- 
ures 3 to 7. The method of hammering will suggest itself in 
each case. Jump and butt welds will have sufficient upset to 
work on, while scarf welds will not unless the pieces are jumped 
or over-lapped considerably. 

Welding Fires, etc. — The ordinary fire used by the smith for 



ZD 



3(1 



Fig. 5. — Jump weld. Fig. 6. — Butt weld. 

his welding is a deep bed of coke. But the fire may be fed with 
hard or soft coal; it may also be a gas or oil flame. 

For blacksmithing, the coke fire is much the best. In this 
fire nearly pure carbon is burned, and the resultant gases are 
carbon monoxid and dioxid. The carbon monoxid and the coke 
are reducing in their action. They will prevent the metal heated 
from oxidizing and will even clean the metal of scale. 



IRON ^ 

Hard coal can be used, but in a small forge it is impossible to 
get a hot enough fire. Soft coal is a poor coal for forge work. It 
has, as a rule, high sulphur, which the hot iron readily absorbs to 
its detriment. While the thick carbon smoke of the flame is apt 
to collect on the iron in an oily soot unless the flame can be kept 
hot enough. 

Gas and oil flames are often used for chain welding and similar 
operations. The gas or oil should be fairly free from sulphur. 

The gas flame is made by in- 

jecting the gas through a large « 

Bunsen burner. Air is intro- 

1 , 1 , , . , Fig. 7.— Cleft weld. 

duced through holes m the 

burner a short distance from the burner end. Or if the gas is 
under sufficient pressure to make a roaring flame, it will take in 
enough air at the end of the burner. The proper mixture gives 
a nearly colorless flame. The quickest and best way to tell if a 
flame is right for welding is to heat in it a small piece of steel or 
soft iron. If the flame has too much air, the metal piece will 
rust and scale off in the flame. If too little air, the soot will 
collect on the metal and it will not heat quickly. Gas flame is 
the most convenient for most purposes. It is easy to regulate 
and can be turned on the iron while welding. In this way iron 
can be welded without flux. When chain is' made the Hnks are 
hung on a bar above a long narrow furnace of fire bricks. The 
flame is played beneath. 

The oil flame is a cheaper flame than gas. It can be manipu- 
lated in the same way as a gas flame. But the oil must be free 
from sulphur compounds to make a safe flame. 

It has lately been tried to burn gases that have been preheated. 
If coal gas, starting to burn at 35 deg. C., will give a combustion 
point of about 2000 deg., then by preheating it to about 800 
deg. C. and burning, there will be a gain of 400 or 500 deg. 
in the temperature of the flame. In other words, the welder 
has boosted his flame up to about 2500 deg., a very respect- 
able temperature. 

The preheating is done by passing the gases through copper 
coils which are nested above the welding-flame flue, and which 
receive the heat from the welding flue. 



O WELDING 

Causes of Poor "Welds. — Suppose we have an iron or steel 
that will weld. There are still many good reasons for discrediting 
the safety of the joint until it has been tested. They are: 

I. Imperfect Contact. 

a. The two surfaces may give the appearance of perfect 
union, but a considerable percentage of the central portion 
may be faulty. For if the metal in course of puddling is not 
relieved of its enclosed slag, this will be finally pressed out into 
thin laminae. These clea\ing planes will be parallel with the 
bar until it is welded, when they will be upset in all directions at 
the joint. A network of such planes now running across the 
bar instead of parallel to it will greatly diminish the tensile 
strength. 

b. Then, again, the smith may carelessly allow some of his 
flux to stay within the weld. All the hammering in the world 



Fig. 8. — Correct shapes for jump Fig. 9. — Incorrect shapes for jump 

and lap welds. and lap welds. 



will not remedy it. In most cases one of the pieces can be 
scarfed or pointed, so that the first contact of the hot pieces will 
be at a central point. As the hammering proceeds, the slag 
will be forced out of the joint as fast as the pieces weld (see 
Fig. 2). This caution applies equally to. the smithed weld or 
the Lafitte joint (see page 158). 

c. Or the smith may not flux his bars correctly, thereby 
allowing unreduced and uncombined oxid of iron to get in the 
weld. It is not a difficult thing to get this rust incorporated in 
the weld, because it is soluble in iron. Dissolved rust makes a 
"burnt" or brittle joint. Clean silica sand is the common flux. 
The smith dips his hot bars into a box of the sand kept near by, 
and often sprinkles a handful over the pieces when hammering 
if the pieces are large. The reaction between the sand and the 
rust is rapid. Iron silicates, easily fusible, are formed. They 



IRON 



7 



cover the fresh iron surface with a thin glass, which prevents 
further oxidation. 

2. Insufficient hammering or ''working''' may account for the 
poor weld. The iron may be perfectly joined, yet the structure 
is weak and uncertain. Wrought iron has a fibrous structure 
similar to wood. The smith must do his best to continue this 
structure through the weld. With a lap weld he can start with a 
heavy upset which can be hammered down. Hammering serves 
the double purpose of consolidating the metal and of laying 
the cleavage planes perpendicular to the blows. Much ham- 
mering is impossible with jump and butt welds. The lapweld- 
ing of wrought-iron pipe and the scarf-welding of chain links- 
must depend on pressure for their perfect finishing. Welds of 
steel cannot often be much benefited by working. Steel is an 
alloy, without structure. To be strong it must be solid and 
homogeneous. Campbell's advice is to keep the critical tem- 
perature high and keep down the silicon and phosphorus when 
choosing your steel. 

3. Too high a heat is responsible for some bad welds. Very 
great heat will unsettle the structure of the iron in the stock a 
considerable distance from the joint. Because the bar breaks 
near, but not on, the joint, is no proof of the soundness of the 
weld. The structure of the iron is impaired wherever the heat is 
beyond the critical point of crystallization of any important 
impurity. By this is meant that if there be an appreciable 
amount of carbon, for example, it will tend to mineralize the iron 
when the latter is cooled down past the crystallization point of the 
first carbon-iron mineral. A number of other impurities, silicon, 
aluminum, arsenic, etc., are presumed to act in like manner. 
So the smith must work his weld and also all of the surrounding 
metal that has been raised above this critical temperature. 
Just what is the critical temperature is unknown to him, because 
it varies with every iron, according to the amount and proportion 
of its impurities. 

Oftentimes welds are made which cannot be worked to 
advantage. Such welds are apt to be weak. The only present 
remedy is to select for such purpose iron as free as possible from 
objectionable impurities. Machine welds, such as small chain 



8 WELDING 

links and small-bore pipe, where the entire piece must be heated, 
are especially subject to this disadvantage. 

4. Large welds are unsafe. 

Just what is the maximum cross-section of practicable welding 
cannot be safely laid down. Welding is not advisable where it is 
difficult to get a good welding heat, to flux properly, to joint the 
pieces well and accurately, or to work the weld when made. To 
weld a ship's sternpost or skeg or rudder-post was a matter of 
weeks of expensive and often hopeless labor before the advent 
of thermit (see page 147). To weld a large driving- rod, an 
embossing die, crushing roll, or propellor shaft was impossible. 
The largest iron pipe used, however, could be welded; also 
chain links a foot or more long, and 2- or 3-inch stock could 
be safely welded. 

Campbell says,^ "Welds of large rods of forging steel are 
entirely unreliable. Electric methods do not offer a solution of 
the problem, for during the process the metal is heated far be- 
yond the critical temperature." Thermit, since discovered, does 
offer a partial solution, because a thermit weld can be reinforced 
with as much metal as needed, and the metal itself can be varied 
to meet the requirements. Its cost is to be considered. The 
oxy-acetylene melt-weld should recommend itself for like reasons. 
More than one torch can be used for large work (see page 75). 

Effect of Impurities, etc. — In order to make a good weld 
of iron, the metal must possess plasticity, which is directly affected 
by the contained impurities. The welding temperature seems to 
be the point at which the iron becomes semiplastic, but is still not 
sufficiently hot to burn or oxidize rapidly. For the reason that 
this temperature varies considerably for the different alloys of 
iron, it is impracticable to make any definite rules. A number of 
impurities or alloy formers affect the welding property to a marked 
degree even when present in fractional parts of i per cent. Sub- 
stances which cause "red shortness," such as sulphur, or which 
oxidize to form an impervious skin, such as aluminum, must be 
avoided in iron. 

In the case of cast iron, which is iron high in carbon and silicon, 
the metal passes suddenly from a crystalline to a liquid condition. 

» "Metallurgy of Iron and Steel " p. 588. 



IRON 9 

It cannot, therefore, be welded over the smith's forge, and can be 
welded only by one of the recent special processes. 

There are an infinite number of kinds of iron, due to the pro- 
portions of the combined impurities and the method of treatment 
during the milling. Each of these so-called alloys will act dif- 
ferently at the welding temperature, while many of them cannot 
be welded by the smith at any temperature. There are a few 
general rules which will help the worker in the ^election of his 
material. But there is so much room for failure in welding the 
best irons that what cannot be blamed on the smith and his 
material must be laid to the devil. 

Carbon in the combined state should be kept below 0.30 per 
cent, because it is a hardener and makes brittle in the combined 
state. Carbon has been found to amalgamate with iron to form 
a number of alloys, which are unworkable in proportion to their 
carbon content. W. C. Unwin^ gives 0.90 carbon as the limit 
for welding iron with silica flux; i.io carbon as the limit with any 
flux. These alloys,^ pearile, martensite, cementite, etc., mineralize 
in the iron and form a granitic structure on cooling. It is likely 
that all of the mineral impurities of iron behave in this manner. 

In the uncombined form, as graphite, carbon does not affect 
the welding property, except that it becomes an enemy to the 
homogeneous structure of the metal, just as does slag. 

Slow cooling, drawing the temper, keeps the combined carbon 
at a minimum. Silicon in a quantity approximately over i per 
cent and aluminum even more potently, also reduce combined 
carbon to graphite. However, the objection to silicon is that it 
makes a brittle alloy, and aluminum oxidizes to the disadvan- 
tage of the metal. Slow cooHng is valueless for the reason that 
welding is done at a high heat, when iron is capable of absorbing 
carbon in greater quantity. 

Hence high carbon in the stock cannot be toned down and 
should be avoided. It should never be above 0.50, and ought 
to be below 0.25 for the best results. 

Silicon causes brittleness, which does not yield to welding 
heat. It must be kept below 0.20 per cent. Silicon is the 

' "Testing of Materials of Construction," W. C. Unwin. 

2 Wm. Campbell, Electrochemical and Metallurgical Industry, Feb., 1904. 



lO 



WELDING 



element which differentiates cast iron from mild irons and steel. 
An iron with gray-colored fracture contains too much silicon to 
use in welding. 

Welding Property of Silicon Steels^ 



The weld 


Si 


c 


p 


s 


Mn 


Unsatisfactory 


0.21-5.08 


0.14-0.26 


0.08 


0.05 


0.14—0.29 


Perfect 


0.01-0.504 


0.I6-0.IS 0.05I-O.I2I 


0.028-0.094 


0.455-0.622 



It will be noted that the second series of steels gave perfect 
welds with a content of 0.504 silicon, by above analysis; prob- 
ably accounted for by the high manganese, which will prevent 
crystallization. 

Phosphorus makes the "rotten iron" for thin and sharp cast- 
ings when present in quantity approximately over o. 10 per cent. 
Malleable iron for welds should contain less than 0.03 per cent 
of it, not so much to assist welding, as to insure a strong joint on 
cooling. 

Sulphur is one of the deadly enemies of the smith. Its effect 
on iron is especially disastrous at welding temperature, even when 
not otherwise apparent. In quantity approximating over o.io, 
it causes " red shortness," brittleness. It should be kept as low as 
possible. Manganese is the remedy for sulphur, used in the pro- 
duction of iron, but the smith cannot correct it with manganese 
himself. Very low sulphur content is the secret of the success of 
Swedish iron in the arts. 

Manganese may be present up to about i . 50 per cent, in iron 
or steel to be welded. Up to this limit its effect is generally 
beneficial. Campbell states that between 2 and 6 per cent it 
forms a brittle unworkable alloy. Hadfeld's steel, with about 
7 per cent, manganese, again becomes malleable. 

Manganese is the cheapest tonic of the iron producer. It 
reduces both sulphur and oxygen in the iron and rises to the top 
as slag. The remainder, if any, forms a tough workable alloy 
with the iron. 

'Campbell, "Metallurgy of Iron and Steel." 



IRON II 

Nickel steel welds readily at all compositions. Nickel is a 
valuable addition to iron, because small percentages of it greatly 
increase the tensile strength without impairing the elasticity. 
It is also valuable because it prevents rust in its iron alloys to a 
marked degree. Nickel steels of from 2.05 to 4.95 per cent 
nickel are specifically mentioned as weldable if the carbon is 
kept down.^ 

Chrome steeP can be welded. The first hammering must be 
very gentle so that the metal will not fly to pieces. 

Aluminum. — There is some uncertainty about the effect of 
small quantities in iron. In amounts above 3 per cent it 
forms a valuable alloy with steel, which is highly fluid on melting. 
0.50 per cent increases the tensile strength and elastic limits 
from 3000 to 8000 pounds and lessens the ductility.^ Odel- 
stjerna^ says that only 0.002 aluminum gives inferior steel 
castings, the fracture being coarsely crystalline. 

A serious count against aluminum, if it be true, is that it 
oxidizes in its alloys and coats them with a skin. This would 
seriously affect the welding, because this skin is a very refractory, 
unmanagable substance. Reliable data are wanting. 

Copper is generally believed to be harmful in malleable iron. 
However CampbelP in his welding experiments used bars con- 
taining 0.35 per cent, with excellent results. He says: "The 
critical temperature at which the steel ceases to be malleable 
and weldable varies with every steel. It is lower with each 
associated increment of copper; it is higher with each unit of 
manganese, and it is lower in steel that has been cast too 
hot." 

Arsenic steel, with less than 0.20 per cent arsenic will weld 
as usual. Between o. 20 and i . 20 per cent a flux of borax and 
sal ammoniac is needed. 2.75 per cent arsenic prevents welding 
altogether, and the iron behaves hke pig iron.** Campbell claims 
that so small an amount as 0.093 impairs the welding property. 

^Iron Age, July 25, 1905. 

^ R. Brown, Journal of the Iron and Steel Institute, i8q6, Vol. I, p. 472. 

^"Metallurgy of Iron and Steel," Wm. Campbell, p. 477. 

* Transactions American Institute Mining Engineers, Vol. XXIV, p. 312. 

^ "Metallurgy of Iron and Steel," p. 467. 

® Iron Age, April 13, iSqq. 

^ "Metallurgy of Iron and Steel," p. 478. 



12 WELDING 

He says that o. 20 per cent, of arsenic increases the strength and 
reduces toughness. 

Nitrogen content is not a subject for the smith to bother about. 
Nitrogen has been blamed recently for otherwise unaccountable 
failures of chemically good iron. E. J. Sjostedt^ claims that 
infinitesimal quantities of it cause red and yellow shortness. He 
claims that a furnace producing trisilicate slag gave iron with 
0.003 P^r cent nitrogen; bisilicate slag, 0.016 per cent nitrogen; 
monosilicate slag, .024 per cent nitrogen. 0.006 per cent, he says, 
is the limit for good steel and, presumably, for good welding steel. 

However, there is at present no easy way of recognizing its 
presence, and it cannot be guarded against. 

Tests of Smith Welds. — Campbell made a series of tests of 
smithed welds of all of the different kinds of steel and of wrought 
iron, the results of which are given in tabulated form in his 
"Metallurgy of Iron and Steel." Four smiths of ability and 
experience welded the metal in flats and rounds of size and shape 
most convenient for handling. And though the men knew their 
bars would be tested, their welds were often far from satisfactory. 
"Picking out the worst individual weld of each workman, black- 
smith 'A' obtained only 70 per cent, of the value of the original 
bar, 'B' 54 per cent., 'C 58 per cent., and 'D' only 44 per cent. 
The forging steel showed one weld with only 48 per cent., the 
common soft steel 44 per cent., while even the pure basic steel gave 
one test as low as 59 per cent." 

But the tensile strengths of the bars are fairly uniform when 
compared with the elongation. "In some cases where the break 
took place away from the weld, the elongation was nearly up to 
the standard." The elongation test of a basic open-hearth steel 
of low carbon gave greater elongation in welded pieces than in the 
natural bar; "but in the other pieces the stretch was low and the 
fracture so silvery that it was plain the structure of the bar had 
been ruined. In most cases where the test bar broke in the weld, 
the pieces parted at the surfaces of contact, showing that no true 
union had taken place; one or two fractures were homogeneous, 
but they showed the coarse crystallization that follows over- 
heating." ^ 

* Iron Age, May 5, 1904. ^ "Metallurgy of Iron and Steel," Wm. Campbell. 



IRON 



13 



Welding Tests of the Royal Prussian Testing Institute 


1 


Kind of metal 


Ultimate strength 
lb. per sq. in. 


Per cent, elonga- 
tion in 20C mm. 

= 7.87'' 


Per cent, of 
reduction of area 


Average 
of 6 tests 
natural 


Average 
of 9 tests 
welded 


.Average 
of 6 tests 
natural 


Average 
of 9 tests 
welded 


Average 
of 6 tests 
natural 


Average 
of 9 tests 
welded 


Medium O. H. steel . 

Soft 0. H. steel 

Puddled iron 


72110 
64570 
57890 


41820 

45800 
47080 


20.8 

25-1 
22.2 


3-2 

5-1 

7-7 


34-9 
44-7 
39-5 


4-5 
10.5 
14.0 



These results agree substantially with those of Campbell. 
The lowest result for soft steel was ^^ per cent., the average 71. 

The lowest result for medium steel was 23 per cent., the 
average 58. 

The lowest result for puddled iron was 62 per cent., the aver- 
age 81. 

These results confirm the general impression that puddled 
iron is the best iron for welding. Contrary to one authority who 
says that iron before puddling welds more easily because of the 
presence of the slag in the iron. 

The welding tesf- is occasionally specified in this country on 
account of the common use of welds in structural work. Two 
iron bars of the metal under test, of about i inch section, are 
scarfed, heated to white heat, and joined without flux. The 
joint is worked with an 8- or lo-pound hammer, and brought 
down to unit section. It is cooled without chiUing. This bar 
is then tested for tensile and elastic strength; and a similar weld 
is half cut open, bent until fractured, and examined for structure. 
Results of Tests by Prof. Bauschinger 



Kind 


Section, sq. in. 


Ratio of strength at weld to 
strength of bar, per cent. 


Soft steel and ingot iron. 
Wrought iron 


0.15 to 2.00 
0.15 to 2.00 


89, mean, 57 to 105, range 
95, mean, 83 to 102, range 



' Journal of the Iron and Steel Institute, Vol. I, 1883, p. 425. 
^Transaction of the American Institute Mining Engineers, Vol. II, p. 628. 



14 



WELDING 



Welds made with steam hammer were lo per cent, stronger for 
mild steel and 5 per cent, stronger for wrought iron on the 
average than hand welds. 

Results of Tests by W. C. Unwin' 



Percentage of 
Carbon 


Ratio of strength at weld to strength of bar, per cent. 


Series A 


Series B 


0-75 

I.OO 
I.OO 

1-15 
1-15 

1-25 


59 
76 

5° 
89 
75 

75 


68 
51 
84 
113 
117 
86 



Results of Tests by David Kirkaldy & Son- 



Kind 


No. 

of 

tests 


Size of test bar, 
inches 


Ratio of strength at weld to 
strength of bar, per cent. 


Mean 


Range 


Electric weld 


17 


1. 1 29 diam. 


89.1 




Smith weld 


19 


1. 116 diam. 


89-3 






Steel bolts, welded . . 


28 


1 to 2 J diam. 


75-1 


71.5 to 88.8 


Iron bolts, welded . . . 


181 


i to 22 diam. 


73-8 


61.7 to 88.2 


Iron tie-bars, welded. 


18 


i\ to 3.13 diam. 


59 


37 to 74-2 


Iron tie-bars, welded. 


10 


2.5 X (.24 to 68) 


76.7 




Iron plates, welded . . 


7 


10X.87 to 6 X 1. 1 1 


65-5 


57-7 to 83.9 


Iron chain links 


1086 


Yq to 2 (area turned) 


86.4 


72.1 to 95.4 


Bar plate, welded. . . 


14 


4 to I5 thickness 


68.8 


52.6 to 82.1 



"Testing of Materials of Construction," 1899. 
'"Strength and Properties of Materials," W. G. Kirkaldy, 1891. 



PLATINUM 15 

Conclusions. — Holley^ gives three conclusions concerning 
iron: 

" I. None of the ingredients except carbon in the proportions 
present seems very notably to affect the welding by ordinary 
methods. 

"2. The welding power by ordinary methods is varied as 
much by the amount of reduction in rolling as by the ordinary 
differences in composition. 

"3. The ordinary practice of welding is capable of radical 
improvement, the most promising field being in the direction 
of welding in a non-oxidizing atmosphere." 

He gives his maximums for the impurities as follows: P, 
0.317; S, 0.015; Si, 0.321; Mn, 0.097; Cu, 0.45; Ni, 0.34; 
Co, o. 11; slag, 2.262. 

Campbell's deductions are: 

"i. With the exception of manganese in small proportion, 
the usual impurities in steel reduce its welding power by lowering 
the critical temperature at which it becomes coarsely crystalline. 

*' 2. A small content of manganese aids welding by preventing 
crystallization. 

"3. Only the purest and softest steels can be welded with 
any reasonable assurance of success. 

"4. The confidence of a smith in his own powers and his 
belief in the perfection of the weld is no guarantee that the bar 
is fit to use." 

According to Kent:^ " No welding should be allowed on any 
steel that enters into structures." 

PLATINUM 

Though a rare metal, being at this writing more expensive 
than gold, platinum is much used for analytical apparatus. 
Between the years 1827-44 it was used by the Russian govern- 
ment for coinage.^ But it is now largely made into tubes, wire, 

' "The Strength of Wrought Iron as Affected by its Composition and its Re- 
duction in Rolling." Transactions American Institute Mining Engineers, Vol. VI, p. 
loi. 

^ "Mechanical Engineer's Pocket Book." 

^ Roscoe and Schorlemmer, "Treatise on Chemistry," Vol. II, p. 1350. . 



1 6 WELDING 

crucibles, receptacles, etc., to be subjected to high temperature 
and to come in contact with various acids and alkalies necessary 
for rock analysis; also for leading-in wires for incandescent 
lamps and for sparking points for electrical apparatus. 

Platinum melts at 1760 deg. Cent., is seventh in the mallea- 
bility scale and first in ductility (Prechtl). Heated in presence 
of oxygen, it begins to lose weight at 800 deg. Cent, It absorbs 
hydrogen when heated and gives it off again on cooling, and its 
surface becomes rough/ Like iron, it is highly weldable; best at 
white heat, though also at a dull red. It does not oxidize in the 
air, hence needs no flux, though the surfaces should be polished. 

The need for welding platinum sometimes arises, as in the 
case of analysis tubes made of sheet platinum, the joining of tubes, 
wires, etc., and the fabrication of apparatus and the insertion of 
patches in burnt-out crucibles. 

Before a flame intense enough to melt the metal had been 
discovered, the platinum refiner took advantage of the welding 
property in making his ingot. Sponge platinum, resulting from 
the last stage of refining, was heated to redness. It was then 
pressed strongly together to form a cake. The cake was heated 
to white heat and hammered to a compact ingot." 

The oxy-hydrogen blast was applied to the heating process 
about 1847 by Dr. Hare, of Philadelphia; and later the hammering 
was dispensed with and the platinum was simply melted into an 
ingot. 

Platinum was originally soldered with gold or with difficulty 
welded. The oxy-hydrogen flame makes the process much 
easier, as the metal readily melts under this heat. On account of 
its tendency to absorb hydrogen and consequent bubbling of 
the surface, it is necessary to keep a slight excess of oxygen in the 
flame. 

The oxy-acetylene flame would also answer the purpose, 
though it would be necessary to keep a considerable excess of 
oxygen in the flame. Carbon from the acetylene would rapidly 
attack the platinum. 

I am indebted to Mr. E. A. Colby, of Baker & Co., platinum 

' Roscoe and Schorlemmer, "Treatise on Chemistry," Vol. II, p. 1350. 
^ Encyclopaedia Britannica, Vol. XIX. 



PLATINUM 17 

refiners, for the subjoined special information, which covers 
points hitherto untouched in the literature of platinum and its 
allied metals. 

"The oxy-acetylene flame can undoubtedly be used for the 
welding of platinum, but is not by ourselves for the reason that 
the temperature available is far in excess of that necessary, and 
lack of experience leaves us in doubt as to the effect of the by- 
products upon the metal from the acetylene flame. We consider 
the oxy-hydrogen flame far safer and, as the heat is not so con- 
centrated, it is more useful where large surfaces are to be treated. 
Care, however, must be exercised to have the component gases 
(hydrogen and oxygen) present in approximately the necessary 
amounts for perfect combustion. Platinum takes up hydrogen 
at high temperatures and becomes more or less brittle, depending 
upon the amount of hydrogen retained. 

"No flux is required in the welding of platinum or of other 
metals of the same group, osmium excepted. 

"For the same section, the strength of the weld is undoubtedly 
weaker than that of the body of the metal. Just how much 
weaker we cannot state from observation, but, as a welded joint 
is not submitted to the same mechanical working as the body of 
the metal, its strength is not to be considered as equivalent. 
In practice, however, the welded portion is slightly increased in 
section over the body of the metal, and under these conditions 
there is no material difference in the strength. 

"Iridium, osmium, and other metals of the platinum group, 
when present in small quantities, do not apparently increase the 
difficulty of effecting a joint, but the strength of the joint is con- 
siderably less, as alloys of platinum and members of that group 
become more and more brittle with increase of the foreign sub- 
stances. No difficulty, however, is experienced in welding 
iridio-platinum containing as high as 30 per cent, iridium. 
Additions of even minute quantities of osmium to an alloy of 
this composition, however, make it extremely difficult to obtain 
satisfactory results. 

"Platinum can be united to various other metals, such as 
copper, nickel, etc., but it is an open question as to whether the 
union can be considered as a true welding. Undoubtedly, an 



1 8 WELDING 

alloy is formed of the two metals at the surface of contact possess- 
ing sufficient mechanical strength for the purposes for which 
such welds are used. The only illustration of welds of this charac- 
ter are to be seen in the construction of the ordinaTy incandescent 
lamp, in which the copper wires attached to the filaments are 
joined to the platinum wires sealed in the glass by fusing a piece 
of copper onto the end of the platinum wire. This operation is 
conducted in automatic machines, and has proven very satisfac- 
tory for the purpose." 

GOLD 

Gold is the most easily weldable of all the metals. Like lead, 
it can be welded cold and, provided it is free from certain impuri- 
ties, it can be joined at all temperatures. Gold is generally placed 
first in tables of malleability and ductility. These properties 
are destroyed by certain impurities, notably antimony, arsenic, 
and bismuth. One part of bismuth in 1,920 parts gold is alone 
sufficient to interfere with the working properties of gold. 

Pure gold melts at 1062 deg. Cent, and will not oxidize at 
any temperature. Hence the surface will be clean and weldable. 
The welding property is very apparent with gold leaf, which must 
not be allowed to fold on itself lest the surfaces stick together. 
Gold fillings in dentistry are made by the cold welding of gold 
leaf. 

Pure gold is soft and is seldom used in the arts. To render it 
strong and durable for coinage and jewelry, it is alloyed with cop- 
per and sometimes with silver. Thus the gold coins of Great 
Britain contain eleven parts gold and one part copper. Those 
of France and the United States nine parts gold and one part 
copper. For jewelry both copper and silver are used, the purity 
of an alloy being designated by the number of carats of gold in a 
total of 24 carats. 

The gold of coinage and jewelry cannot be joined without a 
flux. The flux may be boracic acid or a solution of zinc chlorid 
and water. In the making and repairing of gold jewelry a mouth 
blowpipe is used for small and delicate work, and for larger pieces 
a gas blowpipe with a foot-pump air-blast or compressed air. 



SILVER 



19 



The flux mentioned is used in case the surfaces oxidize when 
heated. If the gold is so alloyed as to be hard up to the melting 
point, the weld will be a melt-weld. Low-carat alloys melt 
considerably lower than pure gold. Hence the melt-weld would 
be made at about the temperature that high-carat alloys would 
be plastic enough to weld. 

Gold can also be readily welded by electricity. 

For ordinary cheap and quick joining in jewelry, gold is 
soldered with soft solder, a mixture of two parts tin and one part 
lead. The flux is a solution of zinc chlorid in water. Such a 
joint is condemned by the best jeweling practice: the joint is not 
strong; it is a different color than the gold; the solder is apt to 
destroy the strength of the gold at the joint. 

The following table of hard solders, given by Gee,^ are yellow 
alloys of high melting point and make strong solders: 



Kind 


Fine gold 


Fine silver 


Copper 


Best solder 

Medium solder . 
Common solder. 


12\ 
10 

85 


4^ 

6 

6\ 


3 
4 

5 



These alloys are rolled into ribbons and cut up into "pallions," 
or may be applied in dust made by filing. A description of the 
soldering of gold would properly belong to a treatise on the 
goldsmith's art. 

SILVER 

Silver is also a metal of history. The ancient Greeks knew 
of it as the metal electrum, an alloy of gold and silver, of a brilliant 
pink-whiteness. Silver is now used largely as a silver-gold or 
silver-copper alloy, in which the gold or copper is present in 
approximately 10 per cent. Only rarely is the pure metal used, 
as for filigree work or for alkali retainers. 

Pure silver melts at 960 deg. Cent., and is commonly placed 



1 "The Goldsmith's Handbook," G. E. Gee, p. 136. 



20 WELDING 

second in tables of ductility and malleability. It does not 
oxidize in air when heated. All of these qualities point to the 
supposition that it is readily weldable. But though pure silver 
is made into filigree work, it is always soldered. The common 
alloy for jewelry being a combination with copper would suggest 
at once that soldering or brazing is necessary. In recent years, 
however, silver has been successfully joined in the electric welder, 
both to itself and to other metals. Because of its high heat and 
electric conductance it requires more current, as is also the case 
with copper. 

The joining of silver to silver is effected in jewelry shops with 
a mouth or gas-air blowpipe and with fine silver as a solder. 
Other solders are alloys of silver and copper; silver, copper, and 
zinc; and silver, copper, zinc, and tin. These alloys are given in 
order of their melting points, the most refractory first. The 
flux is borax. 

It would be well to bear in mind that tin is even more harmful 
to the working properties of silver than it is to gold and aluminum. 
Even fumes of tin will alloy with silver and make it brittle. For 
this reason tin should not be used in solder. 



ALUMINUM 

Aluminum is one of the youngest of the metals. It was 
discovered by Woehler in 1827. At first its considerable expense 
prevented its being generally used. About 1889, however, the 
discovery of new processes for its reduction from bauxite, etc., 
cheapened aluminum, so that it has become a commercial metal. 
Since then the expiration of the patents covering many of the 
reduction processes has brought the price still lower. 

Fairly pure aluminum is plastic at ordinary temperature, 
being sixth in ductihty and second in malleabihty.^ It melts 
at 655 deg. Cent.; its plasticity increases with heat up to about 
600 deg. Cent., when it becomes hot short, and will crumble 
under the hammer. It is easiest to work between 350 and 400 
deg. Cent. Its tensile strength runs from about 14,000 pounds 

^ Aluminum Company of America. 



r 
i 



ALUMINUM 21 

per square inch for cast bars up to 50,000 pounds per square 
inch for rolled metal and wire. 

It was at first thought that its lightness (sp. gr. 2 . 6) was its 
most valuable property. But the experimenters soon found that 
it formed valuable alloys. The aluminum bronzes, aluminum- 
iron (about 7 per cent.), and some of the three- and four-metal 
aluminum alloys were found to be good metals for castings for 
bearings, and in many instances will eventually displace brass, 
bronze, and even steel. 

Aluminum has two natural disadvantages. It is electroposi- 
tive and it is difficult to weld or solder. As late as 1903, one of 
the prominent periodicals^ said editorially: "Undoubtedly the 
man who discovers a good aluminum solder will make his 
fortune, for it is the want of this accessory that seriously hinders 
the development of aluminum manufactures." 

Pure aluminum does not oxidize at ordinary temperature, 
but when heated becomes coated with a thin film. This film 
is presumably oxid, though it is so thin that not enough of it can 
be gathered for analysis. It adheres closely, is rapidly replaced 
when scraped off, and does not easily flux away. This film 
covers impure aluminum at ordinary temperature, and it is 
claimed that aluminum alloys of small percentage are troubled 
with the surface film. In pouring for aluminum-iron castings 
there must be only one flow: the molten metal is encased in a 
skin which retards it, and would hinder the union of two streams 
in the m.old. 

Being electropositive to all other metals used in the arts, 
aluminum soldered joints are troublesome. Electrolytic action 
sets in, especially when the joint is in contact with water, and the 
metal at the joint disintegrates. For this reason soldered joints 
are unsatisfactory. 

Many solders for this metal have been recently patented. 
M. U. Schoop mentions his collection of 50 as being incomplete. 
Most of these inventions specify a flux that will remove the trou- 
blesome film. The solder is generally an alloy of aluminum with 
zinc, tin, lead, nickel, copper, or silver, or any two or more of 
these metals in varying proportion. The softer of these solders 

' Iron Age, Dec. 31, 1903. 



2 2 WELDING 

are fluxed on with zinc chlorid, mercuric chlorid, tallow, etc.; the 
harder solders are fluxed with fluorspar, borax, lithium chlorid, 
etc' 

Dr. Richards has invented a self-fluxing solder of a tin and 
phosphorus alloy. The phosphorus either reduces or dissolves 
the film that protects the aluminum surface, and the tin afloys 
with the clean surface. This solder is extensively used. The 
present composition of this solder is 29 parts tin, 11 zinc, i 
aluminum, and i phosphor- tin. ^ 

M. U. Schoop, who has also done considerable research work 
in soldering, has patented a flux. It is a mixture of fluorides of cal- 
cium, potassium, or boron and the chlorids of alkali metals, and 
is covered by British Patent No. 24283, Nov. 26, 1908.^ This 
flux may be used before soldering or the cleaned metal may be 
welded without soldering. 

The softer solders are often too weak for good work. 
All of the solders seem liable to electrolysis. The flux, in a 
general way, may vary in constitution, should not contain 
water, and should have a moderately high melting point. It 
should attack the film, but not the metals. Apparently none of 
the solders can be guaranteed to last indefinitely on account of 
electrolysis. 

Prof. O. P. Watts,* of University of Wisconsin, says: "There 
has been considerable trouble with solders containing tin and 
possibly with some others. In some cases destruction may have 
been due to electrolytic action, but in others it appears to be due 
to a slow diffusion of the tin in the solid state, resulting in the for- 
mation of a layer of a very brittle alloy of aluminum and tin, so 
that the joint breaks. This is a slow action and may require 
a year or more for its completion." 

Aluminum, as can be guessed by its properties, is a weldable 
metal, but the tenacious film prevents the natural flow. Accord- 
ingly, a flux such as suggested by Schoop is used to clean the 
surfaces. The pieces of metal to be welded cannot be heated 
above about 600 deg. Cent., because they will be hot-short. 

' "Die Gewinnung des Aluminiums," A. Minet. 

' The Metal Industry, igo6, p. 22. 

^ Electrochemical and Metallurgical Industry, Jan., 1909. 

* Special Information. 



ALUMINUM 



23 



In 1906, W. C. Heraeus/ of Hanau a. M., exploited a method 
of welding aluminum that resembles the smith's treatment of 
malleable iron. It appears, however, that Heraeus' discovery 
was antedated by the work of Mrs. Emme of this country, who 
welded aluminum without melting it as early as 1897. Mrs. 
Emme sued Heraeus for infringement of patent in 1902, won her 
case, and was afterward bought out by him.^ The method as 
described by M. Minet^ is as follows: The two pieces of alum- 
inum to be welded are polished carefully around the ends, and 
the surfaces to come in contact are polished. They are then 
heated with an oxy-hydrogen blow-pipe or Bunsen flame to the 
proper temperature, 400 deg. C. When this correct tempera- 
ture is reached, the two pieces are pressed against each other 
and are hammered and worked as in ordinary welding, the tem- 
perature meanwhile being kept the same. The metal flows 
together at the weld. The success of the operation depends on 
heating in a complete reducing flame to keep the surfaces bright 
and on maintaining the proper temperature. It would take a 
skilled workman. Upon cooling it will be found that the joint 
will withstand concussion tests and sharp changes of tempera- 
ture. Dick patented a somewhat similar process in 1900. 

The limitation of this practice in welding is obvious. It is 
not easy to keep the metal ends in a reducing atmosphere, yet 
they will oxidize rapidly at welding heat in presence of oxygen. 
And, besides, aluminum is a rapid conductor of heat and, like 
copper, the heat will travel from the joint unless the flame is 
very hot. 

Cowper-Coles has also done good work in welding aluminum. 
He has devised a machine in which the bars of aluminum, cleaned 
and faced off square, are placed and clamped. • The bars are 
heated with a benzene lamp, and when at the plastic point are 
squeezed together until the metal at the joint forms a considerable 
blob and the oxid has been forced out of the junction. The 
weld is then quickly quenched with a jet of water and at the 
same time a screen shuts off the flame. This contrivance of the 
inventor's makes a weld that does not have to be worked. 

' I rem Age, Nov. 22, igoo. 

^Special information. 

^"Die Gewinnung des Aluminiums," A. Minet. 



24 WELDING 

Schoop's method is not dissimilar to these three just described; 
only he cleans the oxid with a dissolving flux before welding. 
Thus his process does away with the difficulty of cleaning the 
metal and keeping it clean; the rapid conduction of heat is still a 
difficulty. 

This latter property of aluminum, its high heat conductivity, 
is of least consequence in the oxy-acetylene welding process, 
where the estimated temperature of the flame is 3600 deg. Cent. 
This welding process is especially adapted to aluminum, takes 
less time, and is sure. The metal pieces need no preliminary 
cleaning, though if the body of the pieces is large, as with motor 
cases, it is best to heat the whole casting over a gas flame. This 
because of the expansion and the rapid conducion of heat from 
the fresh weld. The operator plays his flame directly on the 
fracture, using a small melt bar of aluminum to fill up the break 
and to reinforce the weld. Aluminum melts and behaves like 
solder under the flame. The operator gets a good melt at the 
break and works the soft metal in and out with the end of his melt 
bar. This prevents the solidification of any of the oxid film in 
the body of the piece. 

This weld gives a cast aluminum reinforcement that is stronger 
than the body of the piece because it can be reinforced. There 
is no reason why this system of welding aluminum cannot be 
applied in all instances where aluminum is to be welded. There 
are two precautions necessary. Aluminum melts at 655 deg. 
Cent. ; the temperature of the flame is at least 2000 deg. So the 
operator must take care that he does not get his metal too hot, 
or it will run away from the weld. (In the case of mending motor 
cases, the fracture is placed in a horizontal position and backed 
with asbestos paper.) Also, the operator should not use the cus- 
tomary high-oxygen flame. If he does his aluminum will scum. 

As for strength of the welded joint, Cowper-Coles,^ who tested 
twelve consecutive welds of bars, claimed that the metal had not 
deteriorated. All of the bars broke outside of the weld, and also 
outside of the range of high heating. There is no doubt, how- 
ever, that working the metal at the weld is advantageous, just as it 
is with iron, etc. 

' Electrochemist and Metallurgist, Nov., 1903. 



COPPER 



25 



r 



Conclusion. — From the foregoing, it is plain that aluminum 
articles must be either welded or riveted — not soldered. It is 
likely that the manufacturers will soon begin to use this welding 
property of aluminum more extensively. Riveted ware is 
unsatisfactory, because the metal is too soft unless alloyed. From 
the fabrication of kitchen ware to the building up of light, strong 
metal frames, such as for automobiles, welds would be ideal joints. 

COPPER 

Copper is one of the oldest, if not the very oldest, metals of 
history. It was used almost entirely as an alloy with tin or zinc, 
until recent times. The aborigines of North America, however, 
found the pure metal already smelted for them on the shores of 
Lake Superior; and the tools they used we find to-day, made of 
nearly pure metal, mistakenly said to be "tempered by a lost 
process." 

Pure copper melts at 1080 deg. Cent., is fourth in ductility, and 
sixth in malleability.^ If free from certain impurities, such as 
sulphur and carbon, it becomes plastic above red heat. Under an 
oxidizing flame it will burn or scale, and part of the scale will be 
absorbed by the metal surface. 

It is a curious fact that, though copper is a weldable metal, as 
appears from its properties, it is hardly ever welded. The 
common method of joining copper, brass, and bronze has always 
been to solder, braze, or rivet the pieces. The welding property is 
occasionally mentioned,^ but most metal workers are ignorant 
of the possibility. While the effect of impurities on the welding 
property appears not to have been gone into, we may presume 
that the same substances that cause red shortness and assist in 
oxidation are also detrimental to welding; and that electrolytic 
and Lake copper, being nearly pure, are also most weldable. 
"Over-poled" copper, containing carbon, and copper smelted 
from sulphid ores are red-short, and generally unworkable. 

The fact that the welding of copper is almost an unknown art 
is strikingly shown by the fact that, in reply to the query of a 

' Prechtl. 

* American Machinist, Oct. 23, 1902; Schnabel's Metallurgy, p. i. 



26 WELDING 

correspondent, the editor of a leading technical publication 
recently replied as follows: That copper was not weldable; 
that it flew to pieces if hammered when hot; and that it burned 
rapidly at welding heat, and would not braze perfectly. 

The flux for copper welding usually contains borax or boracic 
acid and a phosphate salt. One flux recommended is two parts 
sodium phosphate and one of boracic acid;* another is one part 
yellow potassium prussiate and twenty parts of borax. ^ A 
pinch of rosin is sometimes added to the flux. When using a 
phosphate in the flux care must be taken not to bring the copper in 
contact with free carbon, because copper phosphate will form and 
will prevent sound welding.^ 

To weld, the metal is heated to redness, when it becomes 
plastic. The calcined flux is sprinkled on the surface and the 
pieces are then joined at a yellow heat and hammered together 
as in iron welding. When using a phosphate flux, do not touch 
the copper with coke or charcoal. A gas or oil flame is pref- 
erable, or the pieces can be heated in an electric welder or with 
a high-temperature torch. An ordinary hammer and anvil can 
be used, but on account of the rapid conduction of heat away 
from the joint, a piece of brick or stone can be substituted for 
the anvil and a wooden mallet for the iron hammer. Copper at a 
red or yellow heat is very plastic, if not red-short. So it is well 
to upset the metal considerably at the joint to allow for working 
with the hammer. 

Copper is welded by the electric process, and a melt-weld can 
be made with the hydrogen or acetylene burner. But in either 
case it has been shown that the fibrous structure is destroyed and 
a crystalline joint occurs. As with wrought iron, the copper weld 
must be hammered or drawn to restore the fiber. Copper 
welding is generally considered unsatisfactory, soldering and 
brazing being preferred, as either can be done below the critical 
temperature of crystallization. 

The smith welding of pure copper is considered more difficult 
than the smith welding of wrought iron. And because pure copper 
is inferior in strength to pure iron, it is unlikely that the welding 

' American Machinist, Sept. 25, 1902, 
2 Ibid. 
« Ibid. 



NICKEL 27 

property will ever be generally taken advantage of. But the 
knowledge that copper can be smith welded and that the welds 
can be made of 100 per cent, strength, may be occasionally 
found to be useful in the arts. 

NICKEL 

Nickel is a metal of secondary importance. Its principal 
use is in nickel alloys, notably nickel-steel, in plating, in coin- 
age, and in the chemical reductions which call for apparatus 
made of a metal of inertness similar to platinum, but of greater 
cheapness. 

The pure metal is harder than iron, melts at 145 1 deg. Cent., 
slightly below iron, and is malleable and ductile. It resembles 
iron in being plastic at a bright red or white heat, and is readily 
weldable at that temperature. As the ordinary nickel of com- 
merce is quite brittle, due to its impurities, it is seen that it will 
not weld. The welding property of pure nickel, however, is of 
importance in nickel plating and in making seamed nickel tubes. 

One of the chief objections to nickel plate is its tendency 
to scale or peel off. Electroplated nickel-iron cannot be drawn, 
bent, or hammered with safety, and frequent changes of tem- 
perature will also tend to crack the nickel surface. 

Theodore Fleitmann, of Iserlohn, Germany, took out a 
patent a number of years ago for making nickel-plated iron by 
mechanical means. Sheets of nickel and iron were heated to 
welding heat in an atmosphere of hydrogen, after having been 
polished and fluxed. They were then welded between rolls, 
without coming in contact with the air. By this method the 
natural tendency of both metals to oxidize quickly was prevented. 
At the welding heat the metals alloyed at the contact surfaces, 
and a plate was produced that could be rolled without detriment 
to the nickel surface. 

In 1903, Thomas A. Edison took out a patent for a some- 
what similar idea. The difference was that his nickel was 
electrolytically deposited, the plate was raised to redness in 
hydrogen gas by electric current, and then rolled. At first 
Edison plated iron sheets in a nickel solution, piled them together 



28 WELDING 

in a clay or cast-iron retort, and raised them to bright redness 
in a hydrogen atmosphere. At this temperature the metals 
alloyed and knitted at contact. They were cooled below oxidiz- 
ing temperature in the same atmosphere before a new change 
of plates was admitted. Later, Edison improved his process 
by making it continuous. The iron, in a roll, was passed first 
through a chamber of hot hydrogen, which reduced all oxids 
and gave it a fresh surface. From this first chamber it passed 
into a cooling chamber of the same gas, then through the nickel 
bath, and the wash-tank; thence through a third hydrogen 
chamber, where it was raised to welding heat; and lastly to a 
cooling chamber of hydrogen. The speed was gauged to allow 
each step of the operation sufficient time.-' 

In 1905, the Standard Welding Company, of Cleveland, 
exhibited tubes of pure nickel welded electrically. The tubes 
were strong and the seam was invisible. The present demand 
for such tubes comes from automobile makers, rubber manu- 
facturers for their end tubes, and industrial chemists for non- 
oxidizable tubes, retorts, and crucibles. 

WELDED PRODUCTS 

A great variety of tools, appliances, and parts are welded in 
some stage of their manufacture. Where pieces of metal are to 
be joined, welding is the first resort, soldering a poor alternative. 
As welding is itself a simple process, the chief difference lies in 
the machinery necessary for different work. In a work of 
limited scope it will not be necessary to go into the details of 
the stock welds, but a number of the most important will be 
mentioned. 

The processes of manufacture are in many cases adaptations 
of the recently discovered processes of welding. The electric 
process is far ahead for repeat or "stock" welding. The hot 
flames are best for job work, but are beginning to compete with 
electricity for "stock" work. Thermit is used mostly for job 
welding or repairing, but can also be applied to continuous rail 
or pipe joining. 

' The Metal Industry, Aug., 1904. 



WELDED PRODUCTS 29 

Wrought-iron Pipe. — Pipe welding is about loo years old, 
and at this writing the manufacture of welded wrought-iron 
pipe consumes a large percentage of all the wrought iron made. 
The first pipe was heated over a coke fire and lap-welded in 
sections. After the Napoleonic wars gun barrels were a drug 
on the market and came to be used for water piping. This supply 
seemed to stimulate the demand, and soon after important inven- 
tions began to assist and simplify the original priniitive methods. 
James Russell, who substituted the butt for the lap-welded pipe 
in 1825, may be called the father of the pipe industry. 

Wrought-iron pipes are made in a number of ways. The 
original lap-weld is still used for its strength. Most pipe is 
butt- welded from long scarfs of iron, heated in a gas or coke 
oven, bent round, reheated, and then welded by being drawn 
over a mandrel and through a die of slightly lower caliber than 
the pipe. In this way the edges are squeezed together on the 
outside, while the mandrel pressing on the inside completes the 
weld. A recent invention is pipe made from a spirally wound 
and welded strip of iron. Weldless drawn-steel tubing is also 
finding a market, but so far welded pipe has proved to be cheaper. 
The process is now a continuous one; and electric welded pipe is 
now on the market. 

Welded pipe is made in sizes of from i/8 inch to about 30 
inches internal diameter. Larger than this, it is generally riveted. 
The iron must be of very good quality, quite pure, and low in 
sulphur and carbon. Fifty thousand pounds per square inch 
tensile strength is as high as it is safe to try to use, as stronger 
irons than this give weaker welds. High-carbon irons and steels 
should never be used for pipe, though their initial strength is 
great. Such metal welds poorly and may easily pull apart at 
the weld under great pressure. 

Chain Making. — Chains made of iron links were known to 
the first smiths or workers in iron. And though chain is now 
replaced in many instances by lighter and stronger cables, it is 
one of the staple iron and steel products. One writer^ estimates 
that in 1905 there were in the United States thirty chain mills, 
having a total yearly output of 50,000 tons of chain. 

^ "The Manufacture of Chain," L. B. Powell, Iron Age, Jan. 5, 1905. 



30 WELDING 

The early chain makers often welded their links at the end, and 
even made circular links. But modern practice is to make the 
link an oval and to weld the stock on one side of the link. The 
stock used varies in diameter from approximately i/8 inch to 
over 3 inches, and the links are from 1/2 inch to a foot or more 
long. Safe practice limits the diameter of the stock from ap- 
proximately ^/8 inch to 2 inches, as sizes smaller are apt to 
burn when heated and sizes larger are apt to weld poorly and 
are unworkable. 

Chain is still largely made by hand, and requires skill and care 
for every link. Speed and a uniform product hav'e been developed 
by special machines in late years. The links are now cut from a 
spring-spiral of- the iron, are heated in a gas oven, are welded and 
swaged by a hydraulic press with die of suitable shape. Small 
chain can now be made on an automatic electric welder. 

As with welded pipe, the chain iron should not be of high ten- 
sile strength, about 50,000 pounds per square inch, and should be 
quite pure. The ultimate strength of a chain depends on its 
design and the perfection of the weld. And as life and property 
are constantly at the mercy of just one poor weld, the different 
nations and insurance companies prescribe tests that are approxi- 
mately double what the chain will be allowed to undergo in prac- 
tice. In this country the U. S. Testing Board and in Great Brit- 
ain the British Admiralty Board and Lloyd's restrict the load to 
50 per cent, of the ultimate strength of the weakest link. 

Miscellaneous. — Other stock welds of importance are car- 
riage tires, frames, hub and axle, and also spoke-and-hub. The 
carriage industry is founded on the weldability of iron. 

Cap screws have larger heads of tough steel welded on by 
electricity. There are children's hoops, printers' chases, three- 
ply skate blades, garden rakes, boiler tubing, axe-blades, shotgun 
barrels, iron rings, wire fences. 

The best grade of American anvils are made of a hard quality 
of steel plate welded on to the top of the block, while the anvil 
horn is also welded on. The best plows have welded steel points 
to resist the wear. 

Besides these older products, many of the industries which 
have recently sprung up are using welding apparatus for making 



WELDED PRODUCTS 3 I 

minor parts of apparatus and machinery — the joining of a durable 
well-wearing metal on a softer body, one metal to another, or one 
special casting to another, so as to avoid the use of intricate pat- 
terns. Ship-builders weld constantly, though it is bad practice to 
weld a vital part. Smith welding is used much less than formerly 
on manufactured articles. The patent welding processes are 
cheaper, quicker, and safer and are superseding the old hand 
method. 



Part II— Electric Welding 



GENERAL 



Electric welding processes have been used commercially since 
about 1880, when Elihu Thomson brought out his low-pressure 
resistance machine, invented about 1877. In recent years several 
processes, notably that of Thomson, have become widely known 
for their successful application to rail welding and to repeat 
welding of stock pieces in manufactories, such as wheelbarrow 
spokes, wagon frames, printing chases, etc. Though the several 
processes in which electric current is used in welding are unlike 
in apparatus and application, the basic idea of each process is to 
produce the welding heat by means of resistance to an electric 
current. The different processes are: 

1. La Grange-Hoho process: resistance being set up in an 
electrolyte. 

2. Zerener electric blowpipe: an ordinary electric arc de- 
flected by a magnet. 

3. Bernardos arc-welder: the metal to be welded as the posi- 
tive pole and a carbon negative. 

4. Thomson process: in which internal resistance in the 
metal to be welded generates the heat. This is also called the 
incandescent process. 

The electric welding processes, especially the latter, have fol- 
lowed the adoption of the oxyhydrogen, gas, and oil flames, and 
slightly antedate the oxy-acetylene and thermit welding methods. 
The arc-welding systems have followed the commercial introduc- 
tion of the arc-Hght in 1881. The internal resistance method 
was earlier suggested by the experiments of Joule and Moissan. 
In 1856 Joule welded a bundle of iron wires by burying them in 
charcoal and heating them with current. While in Moissan's 
furnace the resistance of a closed metallic circuit (as well as the 

3 33 



34 WELDING 

arc-furnace) generated the heat for melting refractory metals and 
for making alloys. 

The Thomson process, the oldest and most important, will 
here be last described. 

THE LA GRANGE-HOHO PROCESS 

This process is well called the "water-pail forge," It comes 
from Belgium and has scarcely been tried out. The metals to 
be heated are fastened to the negative pole of the circuit and 
immersed in a bath of an electrolyte, such as potassium carbonate 
solution. The current when turned on flows from the positive 
pole through the solution, and returns by way of the metal piece 
as a negative terminal. The solution begins to decompose, 
depositing hydrogen on the metal piece in a thin film. The 
metal piece becomes red- or white-hot, and is protected from the 
solution by the hydrogen film. As soon as the proper heat is 
reached, as told by the color of the metal, the pieces are taken out 
of the solution, and welded or hammered together on an anvil 
with a hammer. 

The advantage of this process is that the metals are perfectly 
cleansed from grease, dirt, and oxid by the bath, and are protected 
by the hydrogen film. 

The disadvantage is that the heat is not easily controlled. 
While the working of the hot metal must be done by hand in the 
air where the metal will soon oxidize. 

This process is not likely to have a wide industrial application. 

THE ZERENER ELECTRIC BLOWPIPE 

Werderman applied the high heat of the electric arc to 
melting and welding metals. His apparatus was an ordinary 
flaming arc, the carbons being inclined toward each other. The 
flame of the arc was directed away in a point from the carbons 
by means of a blast of air. In a more recent development by 
Zerener the repulsion of an electromagnet in series with the arc is 
used to direct the arc against the work. The following points 
have been charged against this process: 



THE BERNARDOS ARC-WELDING PROCESS 



35 



1. That it is much cheaper than either the oxy-hydrogen or 
oxy-acetylene flames; because the initial cost of the apparatus is 
lower and the cost of the energy 
used is less than the cost of the 
hot-flame gases for the same 
amount of work done. 

2. That the flame is not 
easy to control. 

3. That the flame is satu- 
rated with hot carbon and car- 
bon gas from the pencils. The 
carbon is taken up by the 
molten metal, which becomes 
burnt or brittle. 

4. That the intense light of 
the arc and the high voltage 
necessary make the welding 
rather dangerous to the oper- 
ator. 

5. That only a limited-sized 
flame can be obtained. 

The Zerener arc has appar- 
ently never been tried out in 
this country. Abroad it is 
sometimes used for welding 
rough work, such as broken 
castings and pieces that do not 
need to retain any elasticity. 

In spite of its several limita- Fig. lo.-Zerener blowpipe apparatus. 

tions, the cheapness of operation should recommend it to trial. 




THE BERNARDOS ARC-WELDING PROCESS 

This arc-welding process is an evolution of the electric furnace. 
In the electric furnace of Moissan and others the electrodes were 
both carbon, and the metal to be melted was placed between the 
carbons in the path of the arc. De Meritens substituted the 
metal itself for one of the carbons; and later Bernardos, a 



36 WELDING 

Russian, perfected the process. Coffin has taken out similar 
patents in America, The Bernardos process has been known in 
Europe for more than twenty years, and has recently been intro- 
duced into this country. Welding heat is obtained by the elec- 
tric arc. The metal to be welded or melted is the positive 




Fig. II. — Operator welding with Bernardos arc process. 

pole. The negative pole is a carbon pencil. The current used 
is direct, of 100 to 300 volts, and 600 to 1000 amperes. The 
metal to be welded lies on a metal table to which the positive pole 
is clamped. The carbon negative is placed in contact with the 
metal and the current is thrown on. The carbon pole is then 



THE BERNARDOS ARC-WELDING PROCESS 



37 



withdrawn 2 to 4 Inches, and an arc is sprung, which follows the 
carbon wherever the carbon is manipulated by the operator. The 
greater part of the heat of the arc, about 3500 deg. Cent., is gener- 
ated in the metal or is reflected back on the metal from the arc. 
The apparatus used is as follows: 




Fig. 1 2.— Operator welding with Bernardos arc process. (Courtesy proceedings 
of the Engineering Society of western Pennsylvania, May, 1909, C. B. Anel.) 

1. Generator of direct current of 100-300 volts and 600-iono 
amperes. 

2. A metal table on which to place the work. 

3. Leads, switches, and controlling apparatus for the current, 
carbon pencil. 



38 



WELDING 



4. Protective apparatus for the workman. 

Apparatus and Current. — The Generator. — It is claimed 
by the advocates of this system that good results cannot be ob- 
tained unless current of ample volume and pressure be used. 
Current from power wires is generally inadequate. It is best 
to have a special dynamo of not less than 75 to 100 kw. For 
reasons given below, the current should be direct. Where the 
current supplied is alternating, a direct-coupled motor-genera- 
tor is used to transform to direct current. The motor-generator 

Shunt Field 
■with Rheostat 




Fig. 13. — Diagram of Bernardos arc welder. 



coupling must be flexible to prevent the armature from burning 
out. This generator will be much the most expensive part of the 
apparatus — costing more than all the other mechanism. 

Direct current is much better and cheaper than alternating. 
As is well known, the greatest heat is found near the positive pole 
of the arc. For this reason the metal object to be welded is made 
the positive pole of a direct current. If it were the negative pole, 
more heat would be lost and the carbon from the pencil would 
enter the weld and harden the metal. While if an alternating 
current were used, some of the carbon would enter the hot metal, 



THE BERNARDOS ARC-WELDING PROCESS 39 

while the weld would not receive more than half the heat of 
the arc. 

Table, Switches, Controlling Apparatus, Carbon. — The table 
which holds the work is of cast or wrought iron. The metal 
to be welded is laid on the table, and it is supposed that the 
contact between table and metal will be sufficient to carry the 
current. If the piece of metal is small, the positive lead had bet- 
ter be clamped directly onto the metal instead of the table. 

The switchboard contains a single-throw switch and a 
rheostat connected with grids. Or the rheostat may be made of 
water-barrels with insulated sides and a terminal plate for a 
bottom. The other terminal is also a metal plate suspended over 
the barrel. It is lowered in and out of the water of the barrel. 



Shield 
Lead 




Fig. 14. — Carbon negative pole and shield. 

The trouble with barrel rheostats is that the water is liable to boil 
over under continuous usage, while the barrel hoops will rust rap- 
idly. Circuit breakers should be used to prevent the armature 
from burning out, in case the operator accidentally short-circuits 
by touching his carbon pencil to his work. 

The carbon pencils are made in sizes of 1/4-inch to i 1/2- 
inch diameter by 6 to 12 inches long — of sound carbon. The 
carbon pencil is fixed into an insulated handle. Midway on the 
handle is a round shield to protect the operator from the flame 
of the arc and from sparks (see Fig. 14). 

Workman's Protective Apparatus. — Under this head come 
rubber gloves, a leather or rubber suit or apron, a hood of cloth, 
stovepipe or wood for the head, and a pair of glasses for the eyes. 
Bear in mind that the operator is manipulating a current of high 
voltage and also an arc of great heat and dazzling light. A stove- 



40 WELDING 

pipe hood for the head is rather unsafe because of the danger of 
shock. The eye-glasses had better be double, of red and green 
or red and blue glass, because the light is violent. 

Practice. — In practice the metal piece to be welded is clamped 
onto the metal table. The positive lead is also clamped onto 
the table or sometimes directly to the metal piece. The carbon 
electrode is pressed against the metal piece, and the switch is then 
closed. The operator, clad in his insulated clothing and hood, 
then draws the carbon pencil away from the piece about 2 to 4 
inches and makes the arc. If the arc goes out or is too intense, 
the current is increased or diminished at the rheostat. 

As with the hot-flame processes, the operator now gives his 
arc a circular movement, taking care to keep the pencil at least 
2 and not more than 4 inches from the work. As the metal 
begins to melt, he works it into the weld with a stick of melt bar, 
as in the oxy-acetylene process (see page 97). The weld may 
also be reinforced with scraps of the kind of metal needed. If the 
metal is brass or zinc, it is best to cover it with a layer of the 
proper flux. 

A slight variation of the Bernardos system is practised in 
Sweden in the welding of boiler plate. Instead of a carbon 
negative, a bar of soft steel is used. The bar begins to melt in 
about a minute and is then pressed on to the weld and the cur- 
rent cut off. The joint of the two plates has already melted and 
the bar acts as melt bar. The joint is hammered, and the arc 
is again sprung and more of the bar melted on. 

The details of manipulating the torch and metal in this 
process are not different from the hot-flame processes. Dif- 
ferent metals require different treatment in heating, fluxing, 
and working. Metals that melt to a liquid will have to be built 
up with a luting of clay or bricks. 

It is claimed for the Bernardos process that the metal at the 
weld is not injured by the heat or the current if the operator 
follows directions and uses common sense. Iron welds should 
not be brittle or hard unless the carbon was originally high. 

Samuel McCarthy^ gave the results of comparative tests of 
the tensile strengths of bars scarf-welded and bars electrically 

' "Bernardos Arc-welding," read before the Inst, of Mech. Engineers, England. 



THE BERNARDOS ARC-WELDING PROCESS 41 

welded. The bars were of several different grades of English 
iron and steel, of cross-section 2 by 1/2 inches approximately. 
He claims an advantage averaging 18 1/2 per cent, for the arc- 
welded bars over the smith-welded bars. The arc-welded bars 
ran from 73.6 to 92 per cent, of the strength of the original 
stock. 

The Bernardos process at present is recommended for general 
repair, work, such as boiler-plate repairing, broken castings, 
cracked parts, etc. The process is handicapped greatly by the 
violence of the light and heat of the arc, by the limited size of the 
flame, and by the danger to the operator from the high voltage. 
As with the hot-flame process, the heating effect is purely local, 
and one part of the weld may be getting cold while the other 
part is being welded. Even heating may be obtained by pre- 
heating over a gas flame; freedom from shrinkage strains may 
be had by annealing. The oxy-acetylene flame may be turned 
on the work from several burners at once. But so far there is 
but one arc with each welder. It is not likely that two or more 
arcs will be used together on one job; the only way to increase 
the size of the work to be welded is to increase the carbon pencil 
and augment the current. Such increase has sharp limitation. 

Cutting Metals with Electric Arc. — The Bernardos arc 
is also used to cut metals. Its adaptation to metal cutting is of 
recent date. The arc is held stationary over the plate until the 
metal is melted in one place. This melted metal is ladled or 
poured out of the hole by tilting the plate. To obtain a clean- 
cut hole, it is best to reverse the plate and complete the hole from 
the other side. If the arc can be manipulated on a horizontal 
plane or held underneath the plate, the hot metal will flow out 
of the melt hole of its own accord. A cut in the metal plate is 
made by advancing the arc along the line of cutting as fast as 
the metal melts. 

This cutting property of the Bernardos arc is somewhat similar 
to the oxy-acetylene torch (see page 75). The arc is not so effi- 
cient as the acetylene torch, however. The latter makes a 
cleaner and smaller cut and clears the metal away as the flame 
advances. The cutting arc has been used to cut down the steel 
piers of the Ferris wheel, for thawing the taps of frozen-up blast 



42 



WELDING 



furnaces, for cutting off parts of castings, and also for mending 
cracks in castings. 

Mr. Auel^ gives the following table of data for the cutting 
arc as approximate: 

Bernardos Process, Burning Hole in Wrought-iron Plate- 



Line volts 


Amperes 


Volts across 
rheostat 


Volts across arc 
including carbon 


I20 (open circuit) . . 
08 








430 
400 

370 
1000 (kick) 
1000 (kick) 


23 
22 
20 
24 

35 


72 
81 
86 
60 
63 


102 


104 

S? 


87 



THE THOMSON PROCESS 

"This process differs radically from all the others in forcing 
through the metal to be heated electrically such volumes of current 
that its own resistance is sufficient to bring every molecule of the 
section traversed by the current to the desired temperature."^ Cur- 
rent is taken from a lighting or power circuit, is stepped down 
to the required 3 or more volts and higher volume, and is 
passed through a secondary circuit in which the greatest resist- 
ance is offered by the pieces of the metal to be welded. The 
cross-section and unit resistivity are so proportioned to the flow 
of current that the resistance produces red or white heat at the 
point of welding. The hot metals are then forced together and 
the weld is made. The apparatus necessary are: 

1. A generator of alternating current. 

2. A step-down transformer, carried in the body of the welder. 

3. Apparatus for regulating the current, and sometimes 
apparatus for automatically shutting off the current as soon as 
welding heat is reached. 

' "Arc Welding," C. B. Auel, Proceedings of the Engineers^ Society of Western 
Pennsylvania, May, igog; presented before the Society, April, 1909. 

^ Size of hole = if inches diameter by i\ inches deep. Size of carbon = ii 
by 6 inches. Time = 3 minutes 30 seconds (includes 45 seconds for reversing plate). 

^ Hermann Lemp, The Engineering Alagazitie, Aug., 1894. 



THE THOMSON PROCESS 43 

4. Clamps for holding the metal to be welded and to transmit 
the current to it. 

The Thomson process presents a number of decided advan- 
tages. Among them: 

1. It is at present the best all-around welding machine for 
welding continuous runs of one weld, such as printers' chases. 

2. The power used is claimed to give a 75 per cent, heat 
efificiency; the powTr is used only as long as needed, and is turned 
off as readily as the hot-flame welding burners. 

3. The heating is rapid, even, entirely local, and is under 
control. 

4. There is no excessive heating as with the electric arc; 
hence no excessive oxidation or decarbonizing of the metal. 

5. The clamps hold the work in accurate alignment and 
furnish pressure enough to squeeze well the hot metal. 

6. The workman is in no danger of injuring his eyes by 
excessive light, nor is the current at all dangerous. The operator 
works without dark glasses or protective apron and can hold the 
metal bars while the welding is going on. 

The present limitations of the process seem to be: 

1. Though it will weld odd or job work, it is practically 
limited to continuous welding of one article, known as repeat 
welding. 

2. Though such metals as brass and cast iron can be welded 
on the Thomson machine, the company does not recommend 
it for such metals as have a marked melting point and which 
are not plastic below that point. High-carbon steel does not 
give an altogether satisfactory weld with this process. 

3. The machine demands power at irregular intervals. 
For this reason station engineers may object to having a single 
machine of large size on their lines. 

Apparatus and Current. — The Generator. — Welding work 
can be done with current from city hghting circuit or the firms 
will sell a generator built for the purpose. A machine built 
for sizes of iron and steel not more than 1/3 inch square may 
be connected to the city alternating lighting wires at 54 or 104 
volts, requiring no transformer. For work larger than 1/3 inch 
square section it is best to get the alternating generator made 



44 



WELDING 



for the machine. The following is a table of dynamos especially 
adapted to welding: 

Generators Specially Adapted for Electric Welding, 220 to 3300 Volts 
(Warren Electric Mfg. Co.) 



K W 


R.P M 


Approx. 


Price 


K. W. 


Exciter 


Standard Pulley 






Weight 


list 


e.xciter 


R. P. M. 


D. F. 


22.5 


900 


3100 


1250.00 


I 


1725 


2li 


4^ 


30 


1200 


3200 


1300.00 


I 


1725 


16 


4^ 


SO 


900 


4900 


1700.00 


I 


1725 


2li 


lh 


60 


900 


6500 


1850.00 


li 


1600 


21^ 


10 


60 


720 


8200 


2200.90 


i^ 


1600 


27 


9h 


60 


600 


9100 


2550.00 


li 


1600 


32 


9\ 


75 


720 


9400 


2550.00 


2 


1450 


27 


12^ 


75 


600 


10500 


2800.00 


2 


1450 


32 


12^ 


90 


720 


10800 


2S00.00 


2 


1450 


27 


15 


100 


600 


12000 


3200.00 


2 


1450 


32 15 



In this process alternating current is invariably used, though 
there is no electrical reason why direct current should not be used. 
It is claimed for alternating current that its heating action is 
more uniform. As it flows mostly on the surface of the conductor, 
its heating effect begins and is most intense on the surface. This 
heat is evenly conducted to the core of the welded pieces; thus 
the radiation and conductance are offset. The periodicity of 
the current may vary between 50 and 250. As low as 20 may be 
used. Guarini^ recommends 80 to 250 on welds of 4-inch square 
section, which, however, is larger than work ordinarily welded by 
electricity. The lower the periodicity, the less will be the skin 
effect, and hence the less the tendency for the current to crowd 
toward the outside of the parts to be welded. The Thomson 
machine is now designed for alternating current of 40 to 60 cycles. 

Figure 15 shows the Thomson apparatus diagramatically. 

The Transformer. — Current from a lighting circuit of 54 or 
104 volts can be carried directly to the welding clamps without 

^Scientific Atnerican Supplement, Nov. 5, 1904. 



THE THOMSON PROCESS 



45 



being transformed. Such a welder is called a direct welder, and 
is used for small work only. With current of a 220- or 440- volt 
circuit a transformer is necessary. Besides which, it is safest 
and cheapest to use a current of not more than 4 to 10 volts in 
any event. 

The transformer used is of the core type. It consists of a 
core of soft iron surrounded with the primary and secondary 
coils, the first of which introduces the primary current at rela- 
tively high voltage and low amperage, and the second of which 
leads off the current for the secondary or welding circuit at 




Fig. 15. — Diagram of Thomson electric welder. 



relatively low voltage and high amperage. The secondary 
coil is a solid copper casting encircling the core. In the larger 
machines, the heating effect of the current transformation is 
overcome by passing a steady current of oil over the transformer 
which is encased in a tight box. This oil is either air- or water- 
cooled. 

Figure 16 shows a machine with two transformers, one for 
heating and one for welding. The machine is described as 
follows : 

"There are two separate transformers in the machine, on 
one of which is mounted a gun-metal platen, sliding on the right- 
hand or welding transformer. The left-hand contact, or elec- 
trode, is located between the contacts of the heating transformer 
and is adjustable for any required space between the electrodes 
of the two transformers by a screw at the left of the welder; the 
right-hand platen being moved to and from the left-hand contact 
by the pressure lever at the right. The cam levers, which hold 
the piece to be welded tightly on the electrodes, are fastened to 



46 



WELDING 



the cast-iron bracket, and are adjustable to varying thicknesses 
of stock. 

"The circuit in the transformers is opened and closed by two 
pole break-switches, which are furnished with the welder and 
should preferably be installed at the back of the machine; treadles, 
which are connected by chains to the break-switches, project 
under and at the front of the welder, and are operated by foot. 

" One piece is laid on the terminals of the heating transformer 
in the direction of front to back of the welder, and is securely 




Fig. i6.^Thomson double transformer electric welder, for dash and fender 
frames. The clamping device can be modified to take other right-angle and 
of welds. 



held by bringing forward the cam lever, the circuit is then closed 
by placing the left foot on the break-switch lever, and, while the 
piece is rapidly heating between the electrodes, the other piece 
is laid on the electrodes of the right-hand or welding transformer 
and tightly clamped by the other cam lever. The foot is then 
released from the break-switch treadle of the heating transformer 
and transferred to that of the welding transformer, when the 
second piece, immediately coming to a welding heat, is forced 



THE THOMSON PROCESS 



47 



against the heated section of the first piece by the pressure lever, 
upsetting against and fusing with it. The foot is then removed 
from the break-switch treadle, and the cam levers are thrown back, 
releasing the welded pieces." 

The transformer is the heaviest part of the welding machine. 
So it is placed in the body of the welder frame, underneath the 
clamping table. It thus gives stability to the machine. Figure 
i6 shows the transformers in plain sight. In figure 21 the 
transformer is covered from view in the body. 
Typical Thomson Welders 



Weight in 
pounds 


Floor 


space 


Maximum 
watts 


Maximum area Q" 


H. P. to 
dynamo 


Length 


Width 


Iron 


Copper 


125 
150 
140 

525 

800 

900 

2,200 

2,400 

7,000 


13" 
15" 
13" 
27" 
28" 
32" 
54" 
70" 
90" 


12" 
12" 
14" 
15" 
18" 
20" 
30" 
30" 
36" 


1,000 

2,OCO 

2,000 
5,000 
7,000 
10,000 
20,000 
20,000 
40,000 


•05 
.10 

•30 
•25 
.60 

1-23 
1.23 

3- 


.0209 
.110 

.20 
.40 

.40 
■79 


2 
4 
4 
9 

12 

17 

35 
35 
80 



Regulating Apparatus. — Regulating apparatus includes a 
switch-board on which are assembled a reactive coil, rheostat, 
potential indicator, and fuse blocks and switches; and apparatus 
for automatically shutting off the current of the primary when 
welding heat is reached. 

The reactive coil (Fig. 17) is to control the current at the 
welder when a great variety of sizes is to be welded. It consists 
of an iron base, a copper hood, a switch, and two laminated iron 
cores; the smaller core carries the copper hood and partly rotates 
within the larger core which has four distinct coils wound on it. 
These coils can be connected either in series, series multiple, 
or multiple, by means of the switch in the base, which is operated 
by the handle projecting through side of base. The hood is 
moved over the winding by a worm gear, which is operated by 
the wheel at the front. 



48 



WELDING 



When the switch handle is in position No. i and the hood 
farthest away from the winding, the minimum current is obtained. 
When the switch handle is in position No. 2 and the hood 
farthest away from the winding, the mean current is obtained. 

When the switch handle is in position No. 3 and the hood 
over the winding, the maximum current is obtained. 

The reactive coil also regulates the potential for metals like 

iron, which are good con- 
ductors when cold and be- 
come more resistant when 
hot. 

A fairly efficient make- 
shift rheostat was formerly 
made of a barrel of water 
into which a metal disk was 
lowered and raised. The 
disk served as one pole and 
the bottom of the barrel as 
the other pole. The sides 
of the barrel were insulated. 
Regarding the high peak 
loads caused by a large 
Thomson machine, The Elec- 
trical Times^ has this to say: 
"Central station engineers have hitherto been somewhat 
chary in connecting electric welders of large size to their mains 
on account of the fluctuating nature of the load, although there 
are numerous instances of small welders being so used. A very 
interesting installation has recently been completed in London 
by the Electric Welding Company, Limited, in which a welder 
of 90 k.w. capacity is worked off a single-phase power supply 
at 400 volts. In order to prevent undue fluctuations of voltage 
on the mains, a special substitutional resistance is installed, built 
in three sections, each controlled by a switch, so that one or more 
sections can be put in circuit according to the size of the work 
being welded. A large liquid resistance is also employed to 
prevent an undue rush of current, when the primary circuit 

'September 5, 1907. 




Fig. 17. — Thomson type reactive coil, for 
controlling current in welding machine. 



THE THOMSON PROCESS 



49 



of the welding transformer is closed, the plates being raised and 
lowered by a small motor through suitable gearing. The con- 
trolling switch of the welder is so arranged that when put in the 
'on' position it starts the plate-lowering gear, thus gradually 
cutting out the starting resistance, and vice versa. This plant 
is in continuous operation, and no inconvenience to other power 
users in the neighborhood has been reported. Another welder 
of smaller size has also been connected to this circuit. In this 
case a special economy coil is used as a regulating device. 

''To facilitate the working of electric welding machines on 
polyphase circuits, Professor Elihu Thomson has recently pat- 
ented a method of winding the trans- 
formers to prevent unbalancing the 
phases. This will doubtless lead to 
considerable development in the near 
future, seeing that the power com- 




/ 




.1 B 

Fig. i8. — Two types of Thomson automatic break switches. 

panics' supply mains are available in most manufacturing 
centres." 

On account of the type of welds it handles, the Thomson 
welder is often made automatic. Suppose a welder is being 
fed links of a chain to be welded. If the welder will put through 
each weld automatically, a uniform product will be secured and 
labor, time, and current will be saved. The automatic shut-off 
(Fig. i8, a) is a switch in the primary circuit which is thrown 
open as soon as the clamps move together on the yielding metal. 
The current is not used any longer than is necessary to heat the joint. 

The break-switch shown in figure 18, a is used with the larger 
welders, heavy currents being employed, and should be installed 



50 



WELDING 



at the back of the welder. The switch is out of reach and is 
operated with the foot by the lever; this lever should run under 
the base of the welder, the end projecting at the front of the 
welder at a convenient place for the operator. 

The break-switch shown in figure i8, b is used with the smaller 
welders for wire and thin flat sections, etc., when the weld is 
made instantaneously and should be installed at a convenient 
height against the left of the welder. The switch is operated by 
hand, the lever being pressed down on to the shoulder at the front, 




Fig. 19. — Thomson universal welder with horizontal oblique clamping device and 
hydraulic jack for pipe straight-away and miscellaneous work. 

where it locks, being automatically released when the weld is 
made, by a cut-out device on the welder, a spring throwing up 
the lever. 

When the piece to be welded does not heat evenly, the lever 
should be lightly and intermittently pressed against the shoulder 
without locking, until the heat is evenly distributed, when it 
should be locked, as before stated. 

The Clamps. — The clamps vary in design in different types 
of machines. Figures 16 and 19 show clamps for various work. 
They are generally of heavy copper, to allow for the passage of the 
large volume of current. The clamps are not rigid in a welding 



THE THOMSON PROCESS 



51 



machine^ but are pivoted or mounted on a straight sliding groove, 
and are made to move toward each other by a lever, wheel-and- 
screw, or by hydraulic pressure. Recently the hydraulic pressure 
has been made automatic, so that the machine will throw on its 
own current as soon as the pieces to be welded are clamped, will 




Fig. 20. — Thomson special machine for welding hubs and spo'kes in agricultural 
wheels. Approximate weight 7,500 pounds. 



squeeze the pieces together at the temperature of plasticity, and 
will throw off the current at the same time. 

Where heavy bars are to be welded, and a good electri- 
cal contact is needed at the clamps, the clamps are operated 
hydraulically. 

As will be guessed, the clamps are liable to get very hot, 



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53 



54 



WELDING 



especially on continuous runs of heavy work. As heat affects the 
conductivity of the clamps, they are often water-cooled. 

Some of the automatic machines are equipped with swages 
working between the electrodes. These swages are brought 
together on the weld immediately after the hot metal is upset. 
They compress the upset or bur and give the weld any desired 
shape. Besides which, their pressure amounts to working of the 
metal and makes the weld much stronger. 









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Fig. 21. — Thomson type 5 AA electric welder for copper wire from No. 6 to 
1-4 inch. Time in heating from 2 to 6 seconds. 7500 Watt alternating current, 
not lower than 50 cycles, from 100 to 350 volts. 



Practice. — The operation of the Thomson electric welder 
is very simple, calling for much less skill than the hot-flame 
processes. For stock welds the current is first calculated for the 
size of the piece to be welded and the kind of metal in the piece. 
Tables of current value, cross-section, and time have been worked 
out for iron, steel, brass, and copper (see page 52). The machine 
being adjusted for stock welds will handle them rapidly without 



THE THOMSON PROCESS 



55 



readjustment, much the same as a printing press will run oflf 
many impressions of the same form. 

The operator places his pieces in the clamps, closes the clamps, 
and advances the clamps toward each other until the two pieces 
touch closely. He turns on the current and as soon as the pieces, 
become plastic or semi-molten at the point of contact he turns 
off the current and squeezes the clamps toward each other until 
the pieces become welded and upset at the contact. 

Figure 21 shows a semi-automatic machine. The copper 
contacts, carrying the clamping device, move to and from each 
other: the left is moved by a screw to get the required opening be- 
tween clamps; the right is held apart by the lever. The wire is 
inserted and tightly held in the clamps, the side lever raised, the 
circuit closed through the hand-automatic break-switch in the 
base of the welder, and the pieces, instantly heating at the joint, 
are forced together by the weights; the circuit being automatically 
opened by the adjustable cut-out device. 

In making the joint, the metal is upset, the extent of which 
depends largely upon the weights and the adjustment of the cut- 
out device. 

When full range of sizes is to be welded or when the smaller 
sizes only are to be welded, a current controller is furnished with 
the welder. 





Energy 


Absorbed in 


Electric Weld 


ing- 


-Prof. Thomson' 


s Process 


Iron 


and steel 


Brass 


Copper 


a 

Hi 
u 


Watts in 

primy. 

of welders 


S 
h 


Is 
us 

X2 


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primy. 

of welders 


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33 


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260 


•25 


7500 


17 


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117 


.125 


6000 


8 


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44 


I 




16700 


45 


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692 


•5 


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22 


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281 


•25 


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142 


I 


5 


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55 


39-4 


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•75 


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29 


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508 


•375 


19000 


13 


31.8 


227 


2 




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65 


48.6 


1738 


I. 


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33 


42.0 


760 


.5 


25000 


16 


42. 


369 


2 


5 


34000 


70 


57-0 


2194 


1-25 


31000 


38 


52.0 


1087 


.625 


31000 


18 


51-9 


513 


3 




39000 


78 


65-4 


2804 


^•5 


36000 


42 


60.3 


1390 


•75 


36500 


21 


61.2 


706 


3 


5 


44000 


85 


73-7 


3447 


1-75 


40000 


45 


67.0 


1659 


•875 


43000 


22 


72.9 


872 


4 




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90 


83.8 


4148 


2. 


44000 


48 


73-7 


1947 


I. 


49000 


23 


82.1 


1039 



56 



WELDING 
Iron and Copper 





Sp. heat 


Cond. 


Melting point, 
deg. Cent. 


Arcing volts 


Iron 


O.I 13 


374 


163s 


25 


Copper 


0.095 


898 


1080 


23 



Copper requires two or three times as much power and only 
0.6 time as long time as iron. Rectangular pieces require 
25 to 50 per cent, more power than circular. A machine that 
will weld 2-inch iron will take i 1/4-inch brass and 7/8-inch 
copper. 

As is seen by the tables, the actual time of welding after the 
current is turned on is often less than one minute per weld; the 
advantage of quick handling, automatic clamping, and automatic 
current shut-off are very apparent. With skilled labor and 
automatic machines, many firms are now turning out from 500 
to 3000 welds per machine per ten-hour day. 

For job work the welder is slower and a skilled man should 
be the operator. If he is called on to weld a succession of dif- 
ferent sizes, shapes, and different metals he will have to use his 
gray matter continually in the regulation of the current, clamps, 
and the amount of uspet and time of cooling before removal 
from the clamps. Many firms use this welder for job welding, 
though it is not specially adapted to job work, 

A number of precautions are necessary in the different steps 
of welding. In the first place, the metal should be very clean, 
both at the clamps and at the points of contact where the weld 
is to be made. The metal can be cleaned in a number of ways. 
If the metal pieces are at all oily they are first dipped in a bucket 
of lye and then in a bucket of water. If the pieces have any 
petroleum oil on them, the lye will not clean them, and they must 
first be wiped down with waste. Sand-blasting and tapping 
will remove the scale. Any remaining dirt can be forced out 
into the upset. 



THE THOMSON PROCESS 



57 



Then the clamps must be set Hghtly on the pieces, and the 
contact surfaces must be as large as possible so that there will be 
good electric conductance. If the contact at the clamps is im- 
perfect the clamps will become heated. 

The distance between the clamps varies with the diameter of 
the metal pieces and also with the kind of metal. In a general 
way, the distance between clamps is equal to twice the diameter, 
with iron; is three times as great as the diameter, with brass; and 
four times, with copper. This difference, of course, is caused by 
the higher conductivity of copper, which requires the immense 
volume of 60,000 amperes per square inch of metal. 













































80 








































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n 


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13 3 4 

Area in Sq. in.. 
Fig. 22. — Power and time required to weld iron (Standard Handbook for Electrical 

Engineers). 

Some metals are best heated rapidly. Steel, rolled copper, 
and like metals, which are easily ruined by heat, must be handled 
with care. They must be heated as quickly as possible; and 
they must not be overheated, or they will lose their structure. 
The act of forcing the hot ends together and squeezing the metal 
helps to maintain the structure and prevent crystallization. 
Such metals should be worked or hammered while cooling. In 
welding tool steel the ends are forced together until the over- 
heated metal is all forced out of the joint into the upset. Of 
course, any scale or dirt is also forced out. When copper wire 
is welded, it should be upset and then drawn down to the proper 
gauge. In this way joints of nearly equal strength can be 



58 



WELDING 



made. While quick heating is a good thing, the joint can easily 
be heated so rapidly that it will be overheated. No metal can 
stand overheating. 

Contrary to common conception, the welding heat hnol caused 
by imperfect contact at the joint. The pieces should fit as closely 
as possible before welding. A poor contact will simply delay the 
heating. 

Rapid welding calls for larger dynamo and welder at greater 
cost, but the increased efficiency will more than pay for the outlay. 



50 



40 



SO 



20 



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y 




































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0.2 



0.8 



1.0 



0.4 0.6 

Area in Sq.in. 

Fig. 23. — Power and time required to weld copper (Standard Handbook for Elec- 
trical Engineers). 

Seven-horsepower minutes is given as the approximate figure for 
bringing one cubic inch of iron to welding heat. ^ If the metal 
clamps conduct the heat away rapidly, from 10- to 15-horsepower 
minutes are required. 

All of the metals of commerce have been welded by this process, 
both to themselves and to each other. Those metals which are 
most plastic at welding heat and which have the widest range of 
plasticity will weld the most readily. Metals which oxidize can 
be fluxed with borax, sand, sal ammoniac, zinc chlorid, etc., but 



' The Engineering Magazine, Hermann Lemp, Aug., 1894. 



THE THOMSON PROCESS 59 

in most cases fluxing is not necessary. The oxid at the contact 
can be forced out into the upset. Brass is generally fluxed. 

Prof. Thomson has in his possession a metal bar of 3/8-inch 
diameter which is made of nine different metals welded together. 
However, the Thomson Company does not recommend its 
machine for cast iron or similar metals of well-defined melting 
point and which are brittle up to that melting point. Cast-iron 
pieces can be melted in the welder and their ends stuck together. 
It is necessary to build up a clay or asbestos form around the 
joint so that the metal will not run away when it melts. Brass 
must be treated in the same way. On cooling it will become 
brittle and crystalline. This is a trouble, however, which is com- 
mon to all the welding processes. If you are welding a trouble- 
some metal you may as well expect doubtful results. The weld- 
ing of copper by this process has been a disappointment to some, 
while others claim complete success for their copper welds. It is 
evident that the difference between good and bad welds in many 
instances is due to the skill employed. 

Adaptability. — In the last decade the Thomson or similar 
machines have forced their way into many of the metal trades. 
In factories where stock welds are made, this process is invalu- 
able. There is a long list of implements that are now welded in 
the process of making. Those industries which are most bene- 
fited are the wagon and carriage, bicycle, tools, wire, chain, pipe 
and pipe bending, and miscellaneous, which includes angle 
welding, typewriters, printers' chases, wire fence, tool steel to 
steel, springs, bands and rings, umbrella rods, etc. 

Occasionally the joining of two different kinds of metals or of 
metals of unequal sizes will call forth the ingenuity of the work- 
man. Copper and brass are frequently welded to iron. When 
metals of unequal electrical conductivity are welded, the clamps 
are placed according to the conductivity of the metal. Thus, 
for copper on iron, the iron clamp would be placed one diameter 
away from the end of the iron, and the copper clamp three times 
the diameter away from the end of the copper piece. Copper and 
iron weld fairly well because their melting points are fairly close 
and they will alloy at the contact. On account of the great dif- 
ference in conductivity, however, the iron will become much 



6o 



WELDING 



Clamps Clamps 

I I 2 Diameters 



[ 



Copper 



Jl DiameterL 



hotter than the copper piece, unless the latter is pointed or whittled 
down as shown in figure 24. 

Another problem has been to join a bar of iron to an iron plate. 
In this case, the current, under ordinary conditions, would flow 
off of the surface of the bar on account of the larger area of the 
plate. The bar would become heated only on the periphery of 

the end, and the plate would 
not be heated to redness. To 
prevent the current from 
spreading at the junction, a 
circular channel is cut into 
the plate at the proposed 
junction, as shown in figure 
25. In a similar way a large bar can be butted on to a smaller 
bar by cutting or whittling the end of the large bar. 

Wire factories can butt-weld their wire ends, thus saving waste 
pieces and allowing them to make any length of wire specified. 

The carriage and bicycle trades have been much benefited 
by the Thomson process. Frames, hubs, spokes, steps, etc., are 
welded by this process. In bicycle manufacture, tubes, forks, 
pedals, crank hangers, mud-guards, etc., are welded. Automo- 
bile making is equally dependent on electric welding. 



Fig. 24. — Welding iron to copper. 
Showing adjustment of clamps and shape 
of copper. 



Channel 




Fig. 25. — Showing how a bar is welded to a plate. 



Iron or brass pipe is butt-welded and also heated prepara- 
tory to bending. In England wrought-iron pipes are flanged 
very successfully. 

A number of firms weld printers' chases by this method. The 
bars are held in the hands of the operator, are butt-welded, and 



THE THOMSON PROCESS 



6i 



then right-angled on a frame. The burr or upset is trimmed off 
on a metal saw and ground even on a wheel. 

Chain is being welded by the electrical process; as fast as two 
links a minute can be turned out on the smallest sizes. In this 
case some of the current, approximately lo to 30 per cent./ travels 
around the ring instead of over the joint. This loss of current 
is expensive and stands in the way of the general adoption of this 




Fig. 26. — Thomson specimens. Type bars, steel to brass; angle weld; bicycle 
fork; hoe; corner angle weld; chain, two welds; chain showing fin after welding; 
chain welded and fin removed. 



process to chain welding. But it is also claimed that this short- 
circuiting of part of the current causes the ring to heat suffi- 
ciently to bend with ease when the ends of the link are closed. 
It is claimed that a bar magnet thrust through the link to be 
welded will largely prevent the current from traveling around the 
link. 

In the welding of hoops and rings this same objection appears. 
The loss of current is much less for rings of large diameter and 

' Iron Age, W. S. Gorton, July 27, 1905. 



62 



WELDING 



small gauge, and can be further reduced by placing the clamps 
closer than is the custom. 

Electric welding is much used in the manufacture of projec- 
tiles and the parts of machine guns. A special high-carbon head 
can be welded on to a soft-steel projectile cartridge. 

Brass heads are joined to steel shanks for use in switchboards. 

Garden rakes that were once made of cast iron are now made 




Fig. 27. — Thomson specimens. Tee weld in pipe; furrule; wire handles; 
bicycle head; sheaves; band saw steel automobile rim; pipe; tee weld; wire mesh. 



much lighter and stronger by putting the teeth on a bar. Both 
teeth and bar are of wrought iron or steel, and are lighter and 
much stronger than the old cast rake. 

Wheelbarrows are made of welded-steel wheels and frames. 
In the wheels, the rim is welded into a hoop, and the spokes are 
welded both to the rim and to the hub. 

The heads of cap screws are now successfully welded onto the 
shanks. This allows the manufacturer to cut hi^ thread in the 



THE THOMSON PROCESS 



63 



hard outer layer of steel. Formerly the screw was cut from a 
billet of the diameter of the head. The head was harder than 
the thread which was turned out of the softer metal near the 
core. It is claimed that the increased strength of the thread 
and the decreased cost of turning down the shank offset the cost 
of welding. 




Fig. 28. — Thomson specimens. Printer's chase; carriage rail; bag frame flat; 
T weld; bag frame on edge; dash frame. 

Rail welding was first suggested by Thomson and practised 
with one of his machines. On account of the importance of elec- 
tric rail welding and the special apparatus needed, the process 
will be described in detail. 

The most recent application of the Thomson process is to the 
welding of sheets of metal. Two sheets of steel are lapped 



64 



WELDING 



and welded at regular intervals in points similar to riveting. 
"The method consists in bringing two pointed electrodes against 
the two sheets, or prepared sheets with slight projections, by 
indenting or punching. The current flows through these projec- 
tions which are pressed down flat on the sheet, effecting the weld. 
This method is used in interior furnishings of steel railway cars, 
passenger coaches, steel furniture, sheet-metal ware, etc."^ 




Fig. 29. — Thomson specimen. Automobile clincher rim. 



Locomotive Flue Welder, — The Warren Electric Manu- 
facturing Company has furnished the following description of 
their flue welder, which is especially adapted to the work: 

"The flue welder (Fig. 30) operates from an alternating source 
of electromotive force, and steps the voltage from any convenient 
line voltage down to from 5 to 10 volts on the weld by means of a 
transformer enclosed in the body of the welder. The secondary 
leads from the transformer are connected to two copper contact 
shoes, which hold the ends of the flues to be welded. These 
contact shoes have a copper top clamping piece, operated by cam 
levers, which clamp the flue very securely. The top and bottom 
members of this clamp are cooled by means of running water. 
One of these pipe clamps which hol4^ the shorter end of the flue 
is operated longitudinally by means of a lever, so as to bring the 
ends of the flues into contact under heavy pressure. One of the 
foot treadles operates a switch in the primary circuit for controll- 
ing the heating of the joint. The second treadle operates a die 

' Special information furnished by the company. 



THE THOMSON PROCESS 



65 



which is brought up so as to surround the joint at the time at 
which compression takes place and prevent an external upset 
around the pipe at the joint. This die is also water-cooled. 

" Owing to the circular form of the pipe, the compression at 
the joint produces a pressure on the interior portion of the pipe, 
which increases the density of the metal. This increased density 
resists the tendency to expand internally, as the metal naturally 




Fig. 30. — Locomotive flue welder. 

expands in the direction of the least resistance. It has been found 
experimentally that there is no tendency whatever to an upset 
on the inside of the pipe. When the flues are welded without 
the clamp die, the free flow of the metal is all outward, which 
produces an exterior upset only. 

"The operation of the welder is as follows: 

"The two ends of the flue are clamped in place, and then 
brought into contact by means of the horizontal hand lever. 
The current is thrown on, and the metal at the joint gradually 
5 



66 



WELDING 



brought up to welding heat. Immediately upon reaching the 
welding heat, the current is thrown off, and the dies for controll- 
ing the form of the weld are brought up into contact with the 
work by means of the second treadle. A further movement of 
the horizontal lever is then made so as to produce a very heavy 
compression of the joint inside of the die. After compression 
the die is then released, and also the top clamps, so as to relieve 
the pipe of strains during the cooling of the joint. 

"The advantage of this form of welder is a practically smooth 
joint on the outside of the pipe, which permits the flues after 
welding to be placed in the end sheets of the boiler without 
reducing the upset usually met with on butt-welds made by the 
electrical process. In welding flues electrically, this exterior 
upset is accompanied by an expansion of the pipe at the joint, 
so as to produce an annular groove inside the pipe, which is 
objectionable in boiler flues on account of the accumulation of 
scale therein. This annular groove is of course entirely elimi- 
nated in the flues as welded by this machine." 

Rail Welding by the Thomson Process. — The most im- 
portant single application of the Thomson process has been to the 
welding of street-car rails. Before 1892, all rail welding was done 
by the cast-welding process. Cast-welding is briefly as follows: 

Pressure Bar 
/ ^-- — Pressure Block 




Rail 



Mold 

Fig. 31. — Weld and pressure block in place for cast welding. 



It is desired to save a piece of track from scrapping, that is 
weak at the joints, and whose rail heads have been considerably 
worn. The cast-welder machine consists of two cars. The first 
car contains the sand blast which cleans all dirt from the rail joint. 
A cast-iron mold is then clamped onto the joint, and the ends of 
the rail heads are pressed down by a block which prevents them 
from springing when the joint is cast (see Fig. 31). The second 
car is now moved over the joint mold. This second car contains 



THE THOMSON PROCESS 67 

the melting cupola — a small, coke-fed blast furnace which melts 
down a mixture of charcoal iron and assorted scrap until it is at a 
high temperature. This very hot iron is run into the mold and 
forms a cast-weld around the heads of the rails. Examination 
of this joint shows that the cast iron of the joint and the steel of 
the rail have amalgamated. The cast- weld is still being used, 
though it has strong opponents. As many as 200 cast- welds can 
be made per day. 

In Los Angeles there are several hundred miles of cast- 
welded track that are being displaced as unsatisfactory. Only 
one joint in ten was found to have amalgamated at the so-called 
weld. The result was a loss of electrical conducti^dty of from 
25 to 75 per cent. The cost per cast- welded joint was given as 
roughly $7.00 as against $5.00 to $6.00 for the thermit joints 
which are displacing them. The breakage was said to be about 
two per cent per annum, and track that was welded in cold 
weather broke the least. ''Sun snakes" were a common occur- 
rence, and were prevented by building the paving close to the 
rail. No open rail track can be welded, as it will warp and 
snake. 

Recently the electric roads have begun to adopt the electrically 
welded rail and also the thermit-welded rail (see page 123). 
Welded rails are a great improvement over those joined by fish- 
plates and bonded with copper wire, for conducting the current: 

1. The conductivity of the weld is as good or better than the 
unit section of rail. There is no bonding to come loose or leak 
or be stolen. 

2. The rail will last much longer. 

3. Welded tracks is smoother riding. 

Rails running through city streets are well embedded in the 
street. If the street paving is not a good conductor of heat and 
the extremes of summer and winter temperature are not too great, 
very long sections of track can be welded into one piece without 
fear of pulling loose at the ends or at any of the joints. A section 
of 2300 feet has been solidly joined at Holyoke, Mass. It is cal- 
culated that the coefficient of expansion of steel in such a climate 
would cause a stress of about 16,000 pounds to the inch, while the 
tensile strength of the rail would run well over 40,000 pounds. 



68 



WELDING 



Friction of the pavement against the rail and inertia of the rail 
prevent dragging, and the expansion and contraction are taken 
up by the elasticity of the rail. Rails welded with thermit or by 
electricity are less liable to crack or pull apart at the weld than 
are cast-welded rails. 

The Thomson process was the first process of welding applied 
to the production of continuous rails on electric railway tracks, 

and was introduced by the 
Johnson Company in 1892. 

In 1897, the Lorain Steel 
Company, successors to the 
Johnson Company, improved 
the process and placed it ac- 
tively on the market. Since 
that time it has been made use 
of in almost all the large cities 
of the United States, and the 
company found it necessary to 
double its equipment for this 
kind of work. 

The joint consists of two 
bars welded to the web of the 
rail, one on each side. Three 
welds are made between the 
bars and the rail, one directly 
over the ends of the two rails 
and at each end of the bars. 
The central weld is made first. 
In cooling, the contraction of 
the bars draws the abutting 




Fig. 32. — Thomson special machine for 
welding rails in streets. 



rails together so that no opening remains across the head of 
the rail. 

The apparatus is mounted on four trolley cars, propelled by 
their own motors. The first car carries a sand-blast apparatus 
for cleaning the rails and bars. The welder is suspended from a 
crane projecting from the front of the second car (see Fig. 32). 
The welder itself consists of a "step-down transformer for supply- 
ing current for heating the weld, and hydraulic pressure apparatus 



THE THOMSON PROCESS 69 

for supplying a heavy pressure to the portions to be welded." 
Suitable mechanism is carried within the car for raising and lower- 
ing the welder and to swing it from side to side to engage either 
rail. Coupled to the welder car, the third car carries rotary 
transformer and regulating apparatus for changing the direct 
current from the trolley to alternating current. A switchboard 
with instruments, etc., is also carried in this car. 

The fourth car carries two grinder carriages, one suspended 
over each rail, to smooth down any inequalities that may exist on 
the head of the rail after the joint has been welded and to produce 
a true running surface. 

The process has been successfully applied to all kinds of rail, 
both girder and T-rails. Also to the welding of the "third "or 
conductor rail on elevated and surface lines. 

The process particularly commends itself for use in crowded 
city streets on account of its harmlessness, as it is not affected by 
dampness and there is no danger of explosions, etc., due to sud- 
den rain storms. The apparatus is practically noiseless in its 
operation. 

An interesting application was the welding of the T-rail on 
the surface track on the north and south roadways of the Brook- 
lyn Bridge in 1906. 

The cost of the equipment makes it more desirable for a rail- 
way company to have the welding done for them than to do it 
themselves. 

The apparatus is also made use of for welding heavy copper 
cables to the rails, either for overhead return or around special 
work. As the conductivity of the welded joint is greater than the 
rail, a most perfect system of bonding is thus afforded at the same 
time with the elimination of the joints. 

From ten to twenty welds are made per day by this machine. 
The breakage is said to run less than 5 per cent., and often not 
higher than i per cent. The machines are leased, not sold, and 
the cost must accordingly be figured on the rental, power, and 
labor in calculating the cost per joint. 

Electric Resistance Heater. — Besides its use as a welder, 
the machine may be used as a preheater of metals to be brazed 
or bent. It will sometimes be preferable to braze or solder a 



70 WELDING 

joint, when the two metals cannot be allowed to lose their shape or 
have any of their substance pressed into an upset: the welder 
can then be used as a preheater. The current would be regu- 
lated to bring the metals to a slightly lower-than-welding heat 
and keep them at this heat. In brazing brass, this is the best- 
known method of preheating, because a torch preheater always 
burns out some of the zinc in the brass and oxidizes the copper. 

The Thomson welder may be used to anneal spots in armor 
plate. This is done by connecting the positive to the armor plate 
and pressing the negative clamp against the spot to be annealed. 

Tests. — In general, tests of electric welds show that from 
75 to 95 per cent, of the original strength of the metal is reached. 
In cases where the upset is not cut off, the strength can be in- 
creased above loo per cent. Welds of low-carbon steel and 
low sulphur-and-silicon iron, if well made and worked or drawn 
after working, will approximate loo per cent, in strength. 

It is sometimes asked if the electric current does not damage 
the metal. Electric welding is no more harmful to the metal than 
any other process. In fact, the control of the heat is so exact 
and overheating and reheating so seldom happen, that electric 
welds run uniformly high in tensile and elastic strength. A 
"burned" weld seldom occurs — the oxid at the joint is forced out 
into the upset and ground oflf. It may be emphatically stated that 
the electric-resistance welds are the best yet made. As an in- 
stance, such a misused and overstrained utensil as a printers' 
chase seldom gives at the weld. 

Sir Frederick Bramwell^ states that i i/8-inch round bars 
can be welded in 2 1/4 minutes with an average tensile strength 
of 91.9 per cent., against four minutes' time and 89.8 per cent, 
strength when smith-welded. 

The results of a series of tests of electrically welded metals 
carried on at the Watertown Arsenal" may be abridged as follows : 

Twenty-nine broke at the weld. 

Seventeen within 2 inches of the weld. 

Eleven within the range of moderate heat. 

Two near the grips. 

' "Elec. Engineering Formula," p. 673. 

^ Transactians of the American Society of Mechanical Engineers, 1889, p. 97. 



THE "fHOMSON PROCESS 7 1 

Welds of wrought iron were 5 to 10 per cent, below unit 
strength; fracture fibrous or slightly spongy. 

Welds of steel were from 50 to 80 per cent, less than unit 
strength. 

Copper welded at 5 to 10 per cent, less than unit strength. 

Steel welded to wrought iron at about the strength of the iron. 

Brass gave an uncertain weld with wrought iron and had a 
strength at the weld of 8 1/2 to 16 1/2 tons to the inch. 

Steel welded with German silver with a strength of 20 tons to 
the inch. 

Some welds of steel were about unit strength and some of 
iron were above unit strength. 

A number of these bars had upsets, however, and the upset 
does not seem to have increased the strength very much. 

When electric welding was first tried out there was serious 
complaint that the welds were burnt, spongy, and weak. This 
was due to the fact that the metals were melted together and 
were not worked. The welding machines with automatic swage 
blocks prevent crystallization at the weld, as does also hammer- 
ing after welding. The weld is still liable to be weak on the 
edge of the heating radius. Many joints that will hold at the 
weld will break an inch either side because the heat has destroyed 
the properties of the metal. 



Part III— Hot-flame Welding 



THE OXY-ACETYLENE PROCESS 

General. — Lest the variations in practice and the variety of 
apparatus about to be described should prove confusing, it is 
well to state that the oxy-acetylene welding process depends on 
the high heat of combustion of oxygen and acetylene. The 
apparatus primarily consists of: 

1. Apparatus for storing or generating oxygen. 

2. Apparatus for storing or generating acetylene. 

3. A burner or blowpipe, with leading tubes, for the combus- 
tion of oxygen and acetylene. 

This is the simple story, of which there are many details. 
The advantages and limitations of the processes here described 
are as follows: 

1. The apparatus is fairly light, easily portable, and can be 
installed permanently. 

2. For repair work, the cost is Hght and the results satisfactory. 

3. On account of the intense heat of the flame, any substance 
or metal can be melted locally at once. 

4. The high heat of the flame represents a limitation in so 
far as it is difficult to adjust and dangerous to use unless the 
operator knows his business. 

5. The weld, being a melt-weld, is subject to oxidation and 
carbonization from the flame, and to crystallization on cooling. 

The merits of the oxy-acetylene process greatly outweigh its 
possible faults. There is no process that will compare with it 
for welding job work of all kinds of metals and for repair work. 

The present use of the oxy-acetylene flame in welding and 
autogenous soldering is the outcome of the discoveries of many 
experimenters. It is a step beyond the oxy-hydrogen process: 
the flame has an opproximate temperature of 3500 deg. Cent., 
while the oxy-hydrogen is about 2250 deg. Cent. But this high 

73 



74 WELDING 

heat and the explosive nature of acetylene complicate the prob- 
lem. Special apparatus had to be devised; special instructions 
worked out for its use in practice. As one writer states, its 
practical value was at first overestimated by those interested in 
it. And when obstacles arose their ardor was checked and the 
process suffered a temporary relapse. At the present writing, 
however, the oxy-acetylene process is in a state of rapid develop- 
ment, and it has passed the critical stage. It is a recognized 
repair and welding process. It is being used to weld or solder 
almost all the metals, both to themselves and to one another; 
it is also used to cut through steel and iron plate, bars, etc., with 
six times the rapidity of a saw. 

There are several items in the apparatus for this process that 
have advanced its use. One of them is the compounds for pro- 
ducing oxygen in situ and at less expense than by the ordinary 
electrolytic process. The Industrial Oxygen Company of New 
York sold until recently a powder called ''Epurite," probably 
sodium dioxide, which produced oxygen when wet with water. 
In igo6 the Industrial Oxygen Company withdrew this com- 
pound and advanced a second, called "Oxygenite." Oxygenite 
necessitates special combustion, cleaning and storing tanks, 
but cost of these is small in comparison with the cost of an elec- 
trolytic plant, and brings it into competition with the storage 
oxygen made by the electrolytic and liquid-air processes. 

The Davis-Bournonville Company have recently adopted 
the potassium-chlorate method of generating oxygen in cases 
where tanked oxygen is inconvenient. As with Oxygenite, special 
tanks are required for generating, washing, and storing. Their 
oxygen compound is not combustible and requires the external 
heat of a gas flame. Fuller particulars of these two chlorate 
processes are given on pages 86 and 87. 

Since 1880 industrial oxygen has been sold in increasing quan- 
tities by the firms using apparatus for the electrolysis of water. 
France and Germany have been specially active in projecting 
methods. The processes of Schuckert, Garuti, Schoop, and 
Schmidt are worthy of mention. In late years oxygen obtained 
by the Linde liquid-air process has come into competition with 
electrolytic oxygen. It is most largely used in this country, while 



THE OXY-ACETYLENE PROCESS 75 

the company claims to supply 90 per cent of the world's demand 
for oxygen. 

Acetylene was discovered in 1837. It was first recognized as a 
valuable illuminant, more especially in France, where it is used by 
hundreds of municipal plants at the present day. France is 
also foremost in oxy-acetylene welding inventions, among the 
most important being those of Fouche. 

Acetylene can now be had in two forms: stored acetylene in 
steel cylinders, such as are used for carbon dioxid; and calcium 
carbid, which produces acetylene when wet with water, accord- 
ing to the formula — 

CaC^+H^O-C^H^+CaO. 

Stored acetylene was originally a dangerous commodity. It 
was liable to explode under pressure. The railroads objected to 
handling it. So the acetylene producer, calcium carbid, held 
the market. The gas was generated at the place where it was to 
be used and kept in a tank under less than 10 pounds' head. In 
1897, the acetone-absorption process was patented, and since then 
stored acetylene has been in active competition with the carbid 
(see p. 92). 

At the present writing a repair shop desiring to set up an acety- 
lene welding department is offered a number of alternatives: 

1. The acetylene can be bought in storage tanks or it can be 
generated from the carbid. 

2. The oxygen can be bought in storage tanks or it can be 
generated from Oxygenite or by the other chlorate method. 

3. Oxgyen can be dispensed with and atmospheric air sub- 
stituted. For this purpose a pressure pump and air gasometer are 
needed. Under the second head it might be added that oxygen 
could be produced by the electrolysis of water. But this would 

require a large, costly outfit, running up into thousands. 
Under the third head, oxygen air and acetylene are sometimes 
used in a three-way burner. 

Apparatus and Gaises.— The Torch.— The first oxy-acetylene 
torch was invented by Mr. Edmond Fouche, who at the time was 
general manager of the Campagnie Franjaise de I'Acetylene 
dissous. 



76 



WELDING 



As they were using compressed acetylene in acetone, it was 
very easy with acetylene under pressure to get the proper mixture 
when used with oxygen under pressure. 

A couple of years later Fouche went with another company, 
which was controlled by Javal. But as they were not handling 
compressed acetylene, but only generators using gas under a 
normal pressure, Fouche went ahead and devised a new oxy- 
acetylene burner under the principle of an injector, which with the 
oxygen under pressure coming from a small tube into a larger, 
would produce a suction, by this absorbing acetylene in enough 
quantity to produce a very hot flame. So this is where the first 
two torches originated — high- and low-pressure. 




Fig. S^. — Low-pressure torch for oxy-acetylene. Industrial oxygen company. 



There is a certain defect in both these torches. The high- 
pressure torch mixes in the long tube as the two gases are forced 
together near the handle, and when the tip of the burner gets 
overheated in case of a flash back, you get a back fire in the 
whole length of the tube; in which case, if the operator is not 
quick in cutting off the flow of gases, he runs a chance of melting 
part of his torch. As for the low-pressure torch, the defect is in 
depending entirely on the suction made by the injector, which 
very often does not carry enough acetylene gas, making an oxidiz- 
ing flame which prevents the metal from uniting properly and 
making the weld very weak. 



THE OXY-ACE XYLENE PROCESS 



77 



The house of A. Boas Rodrigues & Company, of Paris, after 
looking over both systems, went to work to devise a third torch, 
which as far as possible would remove some of the objections of 
the high and low pressure. By making a medium-pressure 
injector type of torch, having the acetylene under at least 3 
pounds' pressure or a little more, they could force in a surplus of 
acetylene so as to remedy the defect of the low-pressure system, 
which depended only on the injector. 

Moreover, back-firing was not troublesome in this medium- 
pressure torch, because the gases were mixed an inch from the 
nozzle. If the torch back-fired, the operator could tell at once 
by the roaring sound. If he did not turn off the flame at once, the 




Fig. 34. — High-pressure oxy-acetylene torch and replaceable tips (Davis-Boumon- 

ville Company). 

tip would be burned, but not the torch. The tip could be un- 
screwed and replaced. 

The present low-pressure torch (Fig. t,t,) also mixes its gases 
a short distance from the tip of the nozzle. 

The nozzles of all oxy-acetylene torches suffer in time from 
the intense heat of the flame. Constant back-firing, caused by 
holding the torch too close to the work, will soon burn out the tip. 
Pieces of melted metal will get in the tip, and should be removed 
carefully. The burner is a very sensitive tool. 

The up-to-date torch is a handy affair with cocks at the handle 
end to turn the gases on and off and a small detachable tip or 
burner at the nozzle end. The gases are mixed near the orifice 
in the low-pressure torch. In the high-pressure torch the gases 
are mixed in the tip (Fig. 35). In both torches the acetylene is 



78 



WELDING 



first passed through a packing of asbestos, wire gauze, etc., with 
handle which prevents a flash back into the generator, on the 
principle of the Davy lamp. The torches are in several stand- 
ard sizes, each with five or six graded detachable tips. An 
extra oxygen tube can be clamped on the burner when used for 
cutting metals. Special cutting torches (Fig. 36) are now made. 




Fig. 35. — Diagram of replaceable tip of high-pressure torch (Davis-Bournonville 

Company). 

A new cutting head is screwed into the torch head. The pure 
oxygen jet flows through the center and in front, and behind 
this are two small heating flames, four in all. With this torch 
it is possible to cut in any direction. 

To summarize, there are at present in use in this country three 
torches: 

I. The original Fouche torch, improved, in which the gases 
are mixed as they enter the haft. 





I 2 3 

Fig. 36. — Cutting torch attachment (Davis-Bournonville Company). 

2. The low-pressure torch (also invented by Fouche) in which 
the oxygen injected under pressure draws acetylene with it 

(Fig. 33)- 

3. The high-pressure torch (French medium pressure) with 
acetylene up to 15 pounds and oxygen stepped down from 120 
atmospheres to one or two atmospheres (Fig. 35). 



THE OXY-ACETYLENE PROCESS 



79 



Each torch claims its advantages, and to number them would 
be to simply give the talking points of the competing firms, without 
effect. 



The Low-pressure Torch 


(The Linde Air Products 


Co.) 






Oxygen 


Acetylene 






Blow- 


Approximate 
thickness of 


Approximate 
consumption 


Approximate 
consTimption 


Foot run 


Approximate 
cost per foot 


pipe 
No. 


sheet or plate, 


cubic feet 


cubic feet 


per hour 


run, includ- 


inches 


per hour 


per hour 




ing labor 


3 


A 


4 


2i 


30 


$.012 


4 


A 


6 


3f 


21 


.021 


5 


i 


lO 


6 


15 


•037 


6 


A 


i6 


10 


6 


•125 


7 


i 


25 


15 


4 


.256 


8 


1 


36 


22 


3 


•456 


lO 


i 


45 


2S 


2 


.827 



Note — For copper plates larger blowpipes are required than for steel plates of 
corresponding gauge. 

Another authority estimates 25 per cent, additional of each 
gas for the same thickness of plate. The high-pressure torch uses 
about the same volume of gas, with the oxygen and acetylene in 
the proportion of i . 28 to i. 

Miscellaneous Apparatus. — Besides the apparatus already 
touched on, there are pressure-reducing valves on all of the pres- 
sure tanks. These may be set by the turning of a handle to any 
constant pressure required; the dial shows the pressure (Fig. 38). 

Both systems have water valves in both gas tubes, to prevent 
the back pressure of either gas in case of accident. For instance, 
in the low-pressure system, if the oxygen should accidentally 
flow back into the acetylene tube, it would get as far as the valve 
which would let it out into the air instead of into the acetylene tank. 
This prevents explosions. "The action of hydrolic back-pres- 
sure valve is apparent from figure 37. The cocks on the acety- 
lene pipe from the gas holder is connected to the inlet at B, and 



8o 



WELDING 



Water Priming Cnp 



Service tine Inlet 



the acetylene pipe leading to the blowpipe is connected to the 
outlet C. D is a priming cup through which water can be 
poured into the chamber until it overflows at the cock F. The 
cock on the service line at B must be closed while the chamber 
is being filled with water. When water shows at the cock F, it 

must be closed and the cock at B 
opened. The valve is then in 
working order. 

"The pipe G, leading from 
below the seal at E to priming cup, 
is made of sufficient length to hold 
a column of water equal to the 
pressure in the acetylene holder, 
which would be equal to not less 
than 12 inches of water, and in no 
case should exceed 20 inches. 

"In cases where two or more 
blov/pipes are worked from the 
same acetylene supply pipe, a 
separate back-pressure valve should 
be employed for each welding 
station." 

The companies furnish twenty 
or more feet of hard-rubber tubing, 
wire-wound. 

Goggles for the eyes are ad- 
vised, both to protect them from the bright light and from 
flying sparks. 

Electrolysis of Water. — When water Is decomposed by electroly- 
sis, it gives 2 volumes hydrogen, i volume oxygen. 

The electrolyte is a dilute solution of sodium or potassium hy- 
droxid; oxygen rises from the positive and hydrogen from the 
negative. If the gases are collected as mixed oxygen and hydro- 
gen in the gasometer, it is called detonating gas. This is the gas 
that was first used in the oxy-hydrogen blowpipe (see page 117). 
Detonating gas is handy for blowpipe work, but it is dangerous. 
It is the most readily combustible mixture of the two gases, and 
if the torch backfires there will be an explosion. To prevent 




Fig. 37. — Diagram of safety 
water seal, to protect the acetylene 
supply (the Linde air products 
company). 



THE OXY-ACETYLENE PROCESS 



8i 



this a safety water-seal was introduced in the leading tube, or 
the blowpipe handle contained a chamber packed with fine rods 
or gauze or asbestos wool to imitate the idea of the Davy safety 
lamp. 

The railroads will not handle detonating gas, and it is not 
manufactured except privately. In the electrolysis of water 
nowadays a diaphragm placed between kathode and anode sepa- 
rates the gases. Of these gases the oxygen is of the greater 
commercial importance. 




Fig. 38. — Oxygen constant-pressure regulator. 

Oxygen is colorless, odorless, non-poisonous, and supports 
combustion with hydrogen, acetylene, producer gas, etc. 

Since 1880 rapid progress has been made in the manufacture 
of nearly pure oxygen and hydrogen by the electrolysis of water. 
Abroad, it is the main source of these two gases, especially since 
1900. In America there is but one electrolytic industrial plant. 
The Linde oxygen practically controls the market. 

Among the successful commercial processes in Europe are 
6 



82 



WELDING 



those using the patents of Schmidt, Schuckert, Garuti, Schoop, 
and Hazard -Flamand. The Schuckert apparatus is as follows: 

" It consists of a cast-iron tank, containing a number of cast- 
iron electrodes in various chambers separated by diaphragms, 
extending from the top downward about three-fourths the depth 
of the cell, the gases being conveyed through a pipe system to 
separators, whence the wash-water is returned to the electrolytic 
cells. 

"The electrolyte is a 20 per cent, solution of caustic potash. 
The cells are embedded in a sand layer about 2 or 3 inches in 
thickness, arranged to protect the apparatus from heat radiation, 
the temperature of the electrolyte being maintained at about 
75 deg. Cent. This is said to be the most satisfactory temperature, 
as the lowest voltage is required at this temperature for decom- 
posing the electrolyte. The pressure is from 2 to 3 volts, and 
the various cells are connected in series very much the same as 
a battery of accumulators. The hydrogen and oxygen gases 
when generated at the electrodes are conducted through pipes 
to separate gasometers or tanks for storage." ^ 

From 97 to 99 per cent, oxygen is claimed for this plant, 
which is that of the Schuckert Co., Nurnberg, Germany. 

Another process, the Hazard-Flamand is also described in 
detail in the Electro-Chemist and Metallurgist"^ of the British 
Faraday Society. The table of relative outputs at different 
current values is given below. 

The Hazard-Flamand Cell 



Volts applied 

at voltameter 

terminals 


Current 

in amps. 


Yield of 

0, grams 

per hr. 


Yield of O2 
grams per 

kw.-hr. 


Per cent, of theoretical 

energy efficiency (213.07 

grams per kw.-hr.) 


2.1 

2-3 

2.8 


243 
265 

323 


72.0 
79.0 
96.2 


141-7 
129.6 
106.3 


66.5 

60.7 
50-5 



^Electrochemical and Metallurgical Industry, F. C. Perldns, May, 1906. 
^Electro-chemist and Metallurgist, June, 1904. 



THE OXY-ACETYLENE PROCESS 8^ 

"In considering the fourth and fifth columns, it must be 
born in mind that hydrogen is also liberated, of double the volume, 
but of i/8 the weight. In other words, with an e. m. f . of 2 . i 
volts, each voltameter produces i . 8 cu. ft. of oxygen per hour 
and 3 . 6 cu. ft. of hydrogen, of the respective approximate weights 
of 72.0 and 9.0 grams." ^ The article goes on to state that while 
2 . 1 volts is theoretically most efficient, 2 . 4 gives best practice. 
The oxygen is 99 per cent, pure and the hydrogen in proportion. 

Manufacturers of electrolytic gases claim that their oxygen 
is much purer than that of other processes. Oxygen by the 
chlorate process is contaminated with carbon dioxid, often 
over 10 per cent. Liquid-air oxygen contains from one to five 
per cent, nitrogen. The impurities of electrolytic oxygen are a 
few per cents, of hydrogen, a little chlorin, and water vapor. In 
laboratory determinations these impurities sometimes determine 
which kind of oxygen shall be used. For welding and soldering, 
the gases should be pure for the sake of keeping harmful im- 
purities from burning into the metal. 

The first cost of installation of an electrolysis plant is very 
great and may reach as high as $25,000, exclusive of maintenance 
cost. For this reason 'very few industries would find it worth 
while to install such a plant for welding purposes. In Europe 
these installations are most often separate concerns for the manu- 
facture and sale of stored oxygen and hydrogen. 

For further information about electrolysis of water the reader 
is referred to "The Electrolysis of Water," by Engelhardt, trans- 
lated by Richards, 1904. 

Storage Oxygen. — Oxygen can be bought in steel cylinders. 
There are two industrial processes at present for making oxygen. 
It can be drawn from the atmosphere by the liquid-air method 
or it can be produced by the electrolytic decomposition of water. 
This latter method to which there are many variations is largely 
used in Europe.^ The patents for the former method are owned 
and operated under, in this country, by The Linde Air Products 
Company. 

By the Linde process the atmosphere is compressed by a 

' June, 1904. 
^"Electrolysis of Water," Victor Engelhardt, 1904. 



84 



WELDING 



double-stage pump up to 1800 pounds. This compression raises 
the temperature i deg. Fahr. for every 2 atmospheres pres- 
sure. The compressed air is cooled by ice and salt (for small 
plants) or by ammonia (for large plants). If this air, then, 
at 1800 pounds and about 15 deg. Cent., be expanded, the tem- 
perature will drop considerably. If some is expanded on the 
outside of a cylinder under the same pressure, the air in the 
cylinder will be lowered in temperature and will liquefy because 
it is under pressure. Liquid air consists of approximately 80 
per cent, nitrogen, critical temperature, — 149 deg. Cent.; and 20 
per cent, oxygen, critical temperature, — 119 deg. Cent. The 
oxygen is then separated by fractional distillation similar to the 
rectification of spirits. 

Storage oxygen can be obtained in cylinders of sizes and 
weights shown in the following table: 

Oxygen in Cylinders (The Linde Air Products Co.) 



Contents in 
cubic feet 


Approximate weight 
in pounds (empty) 


Price of cylinder 
with valve 


Rent per week 
after the first month 


5' 

25 

100 


6 

62 
132 


$ 6.50 

8.50 

12.00 

20.00 


$0.50 

0-75 
1. 00 



The oxygen is under pressure of 120 atmospheres. It is 
guaranteed 95 per cent, pure, the residue being nitrogen. As 
nitrogen is inert and not in sufficient quantity to absorb heat or 
retard action, its presence is negligible. 

These tanks may be rented and the oxygen bought or both 
gas and tank bought outright. In either case the company will 
recharge them, subject to certain conditions. On account of the 
very high pressure, the cylinders are annealed at least once in 
four years, and are carefully inspected and labeled on charging. 
Each tank must have reducing valves and, when in use, pressure 
gauges. The railroads receive them charged as second-class 

^This size of cylinder cannot be hired. 



THE OXY-ACETYLENE PROCESS 85 

merchandise, and discharged as fourth class, and also on account 
of the pressure. 

The factor of safety is large with these tanks, but nevertheless 
they must be kept in a cool place. In the heat of the direct sun's 
rays the pressure will greatly increase. 

The present price of this stored oxygen is from two and 
one-half to four cents, depending on the quantity bought. Rent 
is charged on the tanks after the first month. This is exclusive 
of transportation. The advantage of having a large volume of 
oxygen, in small bulk, when a generator is unhandy or expen- 
sive, is very apparent. The principal disadvantage is the possi- 
bility of leakage, which is a variable factor. Datum is not at 
hand, but it is common opinion that tanked oxygen is at least 
five per cent, purer than that produced by the chlorate process. 

Oxygenite. — "Oxygenite" is the name given to the oxygen- 
producing powder sold by the Industrial Oxygen Co. Its main 
constituents are potassium chlorate and manganese dioxid in the 
probable proportion of loo to 13 by weight. To this is added a 
small percentage of carbon in the form of lamp-black, to support 
and assist combustion. The powder is a fine gray sand in texture ; 
wetting it will not diminish its oxygen-producing ability, though 
it will cause it to cake and harden. It is accepted by the railroads 
at the merchandise rates and is safe to handle. 

One pound of Oxygenite when ignited with a match burns 
with the production of oxygen and carbon dioxid, producing 
about 4 cubic feet of the gas. The oxygen is produced accord- 
ing to the reactions 
2KCIO3 +heat = 2KCI +3O2 and aMnO^ +heat = MngO, +0^. 

The principal function of the manganese dioxid is to reduce 
the temperature of occlusion and to prevent the chlorate from 
melting and flashing. As a good portion of the oxygen is con- 
sumed by the carbon, carbon dioxid gas forms a large percentage 
of the resultant gas. This is washed out of the gas by passing it 
through a solution of sodium or potassium hydroxid. The 
reaction continues up to 200 pounds' pressure and takes less than 
three minutes. 

Figure 39 is a diagram of the apparatus in position. It con- 
sists of a combustion chamber, a washing tank in which pebbles 



86 



WELDING 



are drowned in the caustic solution, and a gasometer. The func- 
tion of the pebbles in the washing tank is to cause the gas that is let 
in at the bottom to work its way more slowly to the top and to 
break up the bubbles. Less caustic solution is needed, and such 
a washer takes the place of three washers in which the solution is 
free. 

This process has its own special advantages, though it is 
not cheap. Oxygen can be generated on short notice and at high 
pressure without the aid of a gas flame for heating nor of a pres- 
sure pump. 



a* 






■^s^=^ 




l^^?8&^ 














V 




b 




c 




a 




a" 

4^ 





h' 




^ 


^ 






^c^J^ 





a Generator 

a^ Cover plate 

a-_ Safety valve 
a^-_ Brace 

a'' Tightening Screw 

a5_0utlet for gas 

a" Pipe to cleaning device 

b Washer and cooler 

b*_Inlet for gas 
b-_FuDnell to stopcock 
b?— Drainage tap 
b^Pipe to storage cylinder 

c Storage Cylinder 

e' Entry valve 

c^ Pressure gauge 

c^ Outlet valve to blowpipe 

c''— Fixture for reducing valve 
c^_ Drainage pipe 



Fig. 39. — Oxygen apparatus using oxygenite (Industrial Oxygen company). 

Oxygenite is at present selling at $15 per 100 pounds. 
Since each pound is claimed to- produce 4 cubic feet of oxygen, the 
cost per cubic foot, exclusive of apparatus, operation, and inci- 
dental costs, would be four cents. Storage oxygen is selling at 
present above three cents per cubic foot. While the final cost 
of using Oxygenite is probably greater than storage oxygen, it is 
able to compete with the latter, because it is safer to handle and 
can be kept indefinitely. 

Oxygen from Chlorate. — The Davis-Bournonville Company 
has recently added to its line apparatus for the production of 
oxygen. The method is similar to the Oxygenite process, but 
the oxygen mixture is not combustible; it must be heated exter- 



THE OXY-ACETYLENE PROCESS 87 

nally with a gas flame. This mixture is composed of potassium 
chlorate, 100 parts, and manganese dioxid, 13 parts; both should 
be fairly pure to insure a gas of 97 to 98 per cent estimated 
purity after three scrubbings. 

Figure 40 shows the apparatus in position. The oxygen mix- 
ture is charged into the retort, which should be as full as possible 
to exclude ordinary air. The retort is heated with a slow gas 
flame so that the generation is regular; as the heating proceeds 
the flame is raised to drive off the last of the oxygen. The oxygen 
generated passes through three washer tanks filled with sodium 
hydroxid solution, and then into a gasometer. From the gasom- 
eter the gas is compressed by a two-stage compressor into pressed- 
steel cylinders, at a pressure of 300 pounds to the inch. This 
for the reason that considerable pressure is needed to make a good 
jet flame, especially in cutting metals. 

This method of generating oxygen takes more time than the 
Oxygenite process; and it necessitates a compressor pump while 
the latter does not. The advantages claimed for it are: that 
there is little oxygen lost when the retort is recharged, because the 
pressure is low in all of the chambers; that loss from leakage is 
much less; that the bubbles of gas being much more expanded in 
passing through the hydroxid solution are washed much more 
thoroughly. 

One writer^ estimates the cost of the oxygen mixture, when 
made from fairly pure chemicals, at eight cents a pound. One 
pound producing 4 to 4 1/2 feet, brings the cost of the oxygen 
to about 2.25 cents a cubic foot. This is exclusive of freight and 
operating charges. 

Oxone. — Very pure oxygen can be generated on a small scale 
by wetting sodium peroxid. 

4NaO+2H20 = 4NaOH+0,. 

The Oxone idea is a recent development of an old method. 
The sodium peroxid in fused lumps is delivered in hermetically 
sealed cans to protect it from the moisture. Each pound of 
Oxone produces over 2 feet of the gas, at a price of from 13 to 
20 cents a foot.^ The generator (Fig. 41) is made by the Nel- 

* American Machinist, Henry Cave. 
^Special Information. 



WELDING 




THE OXY-ACE XYLENE PROCESS 89 

son Goodyear Company and sold by the Roessler & Hasslacher 
Chemical Company, 

To make oxygen several holes are punched in the top and 
bottom of the can and it is placed in the generator. The gen- 
erator is filled with water to the mark, closed and the needle 




Fig. 41. — Oxone oxygen generator (the Roessler and Hasslacher Chemical 

Company). 

valve opened. Opening the valve lets water in on the Oxone, 
and oxygen begins to come off. It is claimed to be 99 per cent 
pure; the trace of water vapor is removed by washing, and the 
delivered gas is then practically pure. The safety valve of the 
generator is set at five pounds and the delivery valve at three. 




Fig. 42. — Oxygne burner (the Roessler and Hasslacher Chemical Company.) 

Closing the needle valve stops the generating. Soda lye is the 
by-product. In cleaning out the generator be careful not to 
get the strong lye on the hands nor clothing. 

This oxygen is expensive, very pure, and the apparatus easily 



90 



WELDING 



portable. Hence it can be used to make gas for reinforcing the 
air in submarines or under-ground or underwater workings 
and by jewelers, dentists, assayers, and silversmiths. For 
burning this oxygen the company furnishes a special torch 
(Fig. 42). The other gas of combustion is sulfuric ether; or 
acetylene, gasoline vapor, or coal ras can be used. The oxygen- 
ether flame is ideal for jewelers and dentists. Figure 43 shows 
a handy furnace for melting down metals. 




Fig. 43.— Oxone furnace for dentists and jewelers (the Roessler and Hasslacher 

Chemical Company). 

Acetylene. — Acetylene is a heavy, combustible gas with a 
strong odor, and was first made by Davy in 1837. It is produced 
by the reaction between water and calcium carbid according to 
the formula — 

CaC^ +H2O = C^H^ -fCaO^ 

The principal impurities of the freshly generated gas are 
ammonia and hydrogen phosphid and sulphid. These are 
removed by washing the gas in different solutions which will react 
upon these gases. 

Acetylene is endothermic. So that the great heat of its com- 
bustion is the sum of its endothermic factor and the factor for 
carbon monoxid or dioxid. For this reason acetylene burns 
with tremendous heat with oxygen. The intense white light of 
combustion in air is attributed to the nascent carbon particles. 

Mixed with air, acetylene is explosive between the range of 
2 per cent, gas, 98 per cent, air; and 49 per cent, gas, 51 per 



THE OXY-ACETYLENE PROCESS 



91 



cent air. This is a very wide range and makes the gas a trouble- 
some one unless used with care. The odor, which is attributed 
to a small proportion of hydrocarbons, is offensive, but helps to 
detect leakage. Though there are instances of asphyxiation by 
this gas, it has been shown that pure acetylene is not a poison- 
ous gas. 



Enighit 




l==-4 



Reeiduum Draw-oflF(KjJ 




I'riSS^^H 



Fig. 43a. — Diagram of carbid-feed acetylene generator. 
(Davis Acetylene Company). 



The Acetylene Generator. — In repair shops, where acetylene 
will be needed continually for the work at hand, it is best to 
install an acetylene generator. One of the types approved by the 
underwriters should be selected. It should be placed in a sepa- 
rate shed outside of the shop. This will safeguard the workman 
and the building in case of accident. Nowadays, however, 



92 



WELDING 



acetylene can be used with perfect safety, provided there is ordi- 
nary good sense employed in the installation and use of it. 

There are two general types of generators: one in which 
powdered or granular calcium carbid is fed into water, the other 
in which water is dropped upon the carbid. The reaction gen- 




FiG. 44. — Diagram of hopper and feed mechanism. Davis carbid-feed acetylene 

generator. 

erates considerable heat. This is the element of danger. For 
this reason, perhaps the safer generator is the style first named, in 
which the carbid would be quenched in water while giving off 
the gas. One part of carbid will boil six parts, by weight, of 



THE OXY-ACETYLENE PROCESS 93 

water. Furthermore, water-feed generators give off gas long 
after the water is stopped, and carbid-feed only for a short time. 

Some carbid contains phosphates which are decomposed 
with the formation of hydrogen phosphid. This gas, which 
comes over with the acetylene in small quantities, is said to 
have a bad effect on the metals to be welded. While tanked 
acetylene has been cleansed of both hydrogen phosphid and 
sulphid, the generator acetylene is not. It is important to use 
in the generator a carbid that is quite pure chemically. The 
presence of small quantities of phosphorous can be easily told 
by the white smoke it adds to the acetylene flame. Sulphur 
cannot be so easily detected. 

One pound of lump carbid gives 4 1/2 feet of gas. One 
pound of ground carbid only 4 feet,^ due to previous decompo- 
sition. At this writing the cost of carbid per candlepower- 
hour is about 4/10 cents for a 24-candlepower burner consum- 
ing 1/2 foot of gas hourly.' 

There are a number of good generators on the market, and 
the purchaser can make his choice from them. The Davis 
generator is at present recommended by the Davis-Bournonville 
Company. This is a lump-carbid feeder made in sizes rangiug 
from the portable size, charged with 20 pounds of carbid, up to 
the largest size of 300 pounds' carbid capacity (Fig. 44). Lump 
carbid, i 1/4 by 3/8 inches, is charged into the hopper at the 
top, whence it slides down an inclined plane onto a circular pan. 
This pan hangs on an axle, which rotates it according to the 
working of the overhead motor, and the carbid is brushed off 
the edge of the pan when it rotates. A pressure diaphragm 
controls the feeding apparatus. The operator sets the diaphragm 
for a given pressure by moving a weight along the lever con- 
trolling the diaphragm. The pressure of the gas can be raised to 
15 pounds, is uniform, and is safe-guarded by a blow-off. The 
water levels are also maintained by overflow pipes. The act of 
opening the hopper to charge the machine locks the motor, while 
the position of the motor weight shows at once how much carbid 
is left in the hopper. 

The advantages claimed for this generator are: 

' Rules of National Board of Fire Underwriters. 
^ Davis Acetylene Company, special information. 



94 WELDING 

1. That being carbid-fed, the resuhant gas is always of a 
safe temperature, because of the great excess of water it is 
quenched in, 

2. The use of lump carbid ensures slower generation, which 
takes place after the lumps have gone to the bottom. And lump 
carbid gives at least lo per cent, more gas than the pulverized 
stone. 

3. The feed motor is effective: the carbid cannot be overfed 
and is fed as the gas is needed. 

4. The water levels are automatically maintained. 

5. All parts are accessible. 

6. The charging hopper is perfectly sealed from leakage. 
This generator should be installed in a shed outside of the 

building where the welding is carried on. The shed should 
be of sufficient size to allow easy access to all parts of the generator, 
and should be steam-heated with pipes coming from without, 
so that the water will not freeze up in the winter. No light or 
fire must be allowed in or near the shed, because of danger from 
explosions. The shed should be kept locked and closed to. 
all but the regular attendant, who is an experienced hand. 

Acetylene gas is much more dangerous than the other illumi- 
nating gases, as it will readily explode in mixtures of more or less 
air than the other gases. Accidents are not so common now as 
formerly, but happen often enough to show that there is much 
carelessness in the installation and management of generators. 
The underwriters' associations of this country and abroad are 
very rigid in their specifications concerning acetylene generators. 

Dissolved Acetylene. — Acetylene dissociates at 780 deg. Cent, 
into carbon and hydrogen; under pressure of two atmospheres or 
more, the gas is tricky and is liable to explode. But acetylene 
is readily soluble in a number of liquids, among them acetone. 
Acetone is fairly cheap, inert, and incombustible — very essential 
properties. It boils at 56 deg. Cent., has a strong affinity for 
acetylene, and is not decomposed by it. At atmospheric pres- 
sure and 15 deg. Cent, acetone dissolves 24 times its volume of 
acetylene. At 12 atmospheres, which is the pressure given the 
storage cylinders, it dissolves about 300 volumes of the gas and 
increases in volume 50 per cent. The pressure of such a tank 



THE OXY-ACE XYLENE PROCESS 95 

is doubled with every rise of 30 deg. Cent., while undissolved 
acetylene triples its pressure for each rise of 8 deg. Cent. 

Berthelot and Vielle^ experimented with the solution of acety- 
lene in acetone and found that it could not be exploded with 
an electric spark though under high pressure. Hutton^ says 
that, "In practice 1,000 liters of acetylene carry off the vapor of 
0.06 liter of liquid acetone" — not an appreciable amount. 

All of the above characteristics of the solution recommend 
acetone as a solvent or body for the storage of acetylene for 
commerce. The French government was the first to officially 
recognize acetone storage tanks as safe. The railroads of this 
country now accept the cylinders for carriage as non-explosive. 

Acetone storage was worked out by the Belgian chemists 
Claude and Hesse, and patented by them in 1897. The principal 
difficulty to overcome was the factor of expansion of the solution 
with increased acetylene content, and the corresponding shrinking 
as the acetylene was drawn out of the tank. The cylinder would 
be full at 12 atmospheres and only two-thirds full under normal 
pressure. This meant that a considerable part of the tank would 
contain the gas alone, subject to the danger of explosion. To 
overcome this, the cylinder was filled with a porous or absorbent 
body, which was saturated with the acetone-acetylene solution. 
Porous brick or stoneware of four-fifths porosity was used; 
also charcoal cake, bound together with soluble glass; in this 
country asbestos fiber with soluble glass binder is used. These 
absorbents will all carry from 50 to 80 per cent, of the solution 
per volume. When the acetylene is all drawn off, the tank is 
still perfectly safe and can be recharged simply by passing in 
acetylene under pressure. 

The tanks themselves are pressed-steel cylinders, such as are 
used for soda-water, and are fitted with cocks and a pressure-regu- 
lating valve. They are delivered under 10 atmospheres' pressure, 
and contain about 100 volumes of the gas — considerably below the 
saturation content of acetone at that pressure. They should be 
kept in a cool place, out of the sunlight, because the pressure 
doubles with 30 deg. rise of temperature. If exposed to too great 

' Elec. and Metal. Industry, March, rgoj. 

^ R. S. Hutton, Elec. and Metal. Industry, April, 1903. 



96 



WELDING 



heat, the pressure might rise to the danger point, and an explosion 
take place. 

Acetylene storage tanks are of the following size and capacity : 

Acetylene Storage Tanks' 



Diameter 
in inches 


Length, inches 


Capacity, cu. ft. 


Weight, pounds 


7 


24 


50 


50 


8 


3° 


80 


75 


lO 


3° 


125 


105 


12 


36 


225 


120 


14 


48 


400 


349 


i6 


48 


500 


435 



Carbid will produce about 4 cubic feet of acetylene per 
pound; the present price is below four cents a pound. This 
brings the material cost to about one cent per cubic foot of gas. 
Stored acetylene costs about twice as much, but its adaptability 
is much greater and in many cases much more than nullifies the 
difference. It is claimed to be the purest form of the gas, being 
practically free from sulphur and phosphorus, because it receives 
four to six washings. 

Practice. — The directions for the use of the oxy-acetylene 
flame are few and the process is simple, but it takes a skilled 
workman to get results. Six months' practice is none too long 
before efficiency can be looked for. It is one thing to melt metals 
together and quite another to make a weld of homogeneous metal 
in which strains are at a minimum. The companies print and 
issue directions, which will be here abstracted and added to. 
Beyond that it is a question of individual gray matter. 

The Flame. — The flame is lighted by first turning on the acet- 
ylene, lighting it, and then turning on the oxygen. The acetylene 
burns with a bright, smoky flame. As the oxygen jet increases, an 
indefinite-shaped cone appears at the nozzle; it first has two points, 
one beyond the other. More oxygen reduces it to a clearly de- 

' Henry Cave, The Horseless Age, Dec. 2, 1908. 



HOW TO WELD 



97 



fined single cone of blue flame. If there is too much oxygen, the 
flame will sputter and roar and the point of the cone become 
ragged and violet-colored. For this reason the operator can al- 
ways teU by appearance when his flame is right. It is always 
safer to have too much acetylene, rather than too much oxygen. 
Oxygen will burn and rust the metal; acetylene will keep it from 
burning. 

The low-pressure flame consumes acetylene and oxygen in the 
ratio of I to 1 . 50; the high-pressure in ratio of i to i. 28. 

As to pressure for the gases, the operator will soon learn by 
trial what pressure of oxygen is necessary to use to keep the flame 
from back-firing. The low-pressure torch needs higher oxygen 
pressure to draw in the acetylene; at least 30 pounds for welding 
and 125 pounds for cutting. Pressure is regulated by turning 
on the fufl initial supply of the gases and then setting the con- 
stant-pressure regulators. Different kinds of work may take dif- 
ferent pressures. 

The hottest part of the flame is at the tip of the cone and a 
fraction beyond. Never hold the cone against the work, because 
it will burn the metal. Only the tip should be allowed to touch. 

HOW TO WELD 

To weld, the operator goes over the metal quickly with the 
flame a number of times. This will heat the metal evenly to 
about dull red heat. If the work is stock work and is continuous, 
it will save from 30 to 50 per cent, of time and cost to preheat 
with a coke, gas, or oil fire or with electricity. 

After preheating the seam, the flame is circled about a small 
radius until the metal softens. Metal is added and worked in 
with a "melt bar " and care is taken that the edges of the metal 
are melted and perfectly united. The operator works away 
from his body and finishes the work as he proceeds. With a 
little practice the seam can be made quite smooth and even. 

Cast iron can be easily welded. It melts easily, is very fluid, 

and runs toward the heat of the flame. Some care is necessary 

to avoid its running clear away from the weld. The piece to be 

welded must be held horizontally or the molten metal must be 

7 



98 WELDING 

dammed. The melt bar is cast iron and should be low in sul- 
phur and phosphorus and high in silicon. Flux is sometimes 
recommended, though a skillful use of the flame and stirring 
with the melt bar will serve the purpose. Salt or borax is a 
good flux. 

Preheating is very necessary in treating cast iron. Heat all 
of the casting to dull red, or as much as is necessary to prevent 
cracking. Coke or gas fire is cheapest if there is much welding 
to be done. Slow cooling is just as necessary as preheating. 
Annealing may even be necessary to adjust the strains. 

Wrought iron requires less care in preheating, though this can- 
not be neglected. The melt bar is soft iron. Pure iron is 
sticky and not very fluid. For this reason the softened metal 
can be stirred into place with the end of the melt bar. It is a 
good thing to hammer and work wrought-iron joints while cooling 
so as to build up the structure that the melting has destroyed. 

Steel also works well with this flame. The metal becomes 
soft but does not run. It burns easily in excess of oxygen. 
Cave^ states that auto frames can be welded from beneath with 
the high-pressure torch, because the melted steel adheres well 
and is spread wherever wanted by the flame. He recommends 
commercial soft-steel wire for the melt bar. Low-carbon, open- 
hearth steel is best for the melt bar, because on cooling it is 
more liable to retain its strength. 

Steel welds should also be hammered if possible on cooling, 
and then annealed. Even then a high-carbon steel will suffer 
severely within the heating radius. The weld joint can be 
reinforced, but the heat always extends beyond the reinforce- 
ment. In spite of reinforcing, working, and annealing, high 
carbon and tool- steel joints will lack strength and the elastic 
limit will be lowered. 

Heavy copper articles are seldom welded with this flame, 
though the results are just as good as by electricity. Because of 
high heat conductixity a larger flame or more time is needed, 
and because of the rapid oxidation an excess of acetylene must 
be maintained in the flame. 

Working is very necessary in the case of drawn and rolled 

' Iron Age, Sept., 1909. 



HOW TO WELD 99 

copper, in order to restore the structure; but it would be well for 
the operator to determine whether the copper is cold-short or hot- 
short before hammering, otherwise he may fracture the weld. 

Brass is a special problem. The hot flame begins to volatilize 
the zinc of the alloy before the melting point is reached. Hence 
some covering or reducing flux should be used, such as powdered, 
fusible silicates, borax, glass, etc. The flux melts and covers the 
surface. Bronze needs similar treatment. 

Aluminum is also troublesome because it becomes pasty, and 
when finally liquid will oxidize rapidly. As soon as the metal 
at the joint softens it is added to from the melt bar, and the pasty 
metal is then worked into the seam or patch with an iron spatula. 
Pasty aluminum can be manipulated like solder. When the 
joint cools it will be as strong as the body of the piece, if properly 
worked. If not properly worked, layers of the oxid film will be 
enclosed in the joint and will weaken it. This film will easily 
come to the surface with working. 

Preheating is very important because aluminum also conducts 
heat very rapidly. Slow cooling of castings is necessary to pre- 
vent tension and cracking. Hammering will give a dense, tough 
structure, but the operator must beware not to hammer aluminum 
between 600 deg. Cent, and 655 deg. Cent., the melting point, 
because it will crumble under the hammer. 

Other metals and alloys can be welded, and will be in the future 
as this process becomes better known. In automobile and ma- 
chine repair shops a great variety of new alloys are constantly 
coming up, and the repair man finds that each requires indi- 
vidual treatment, both in handling the flame and in the use of 
fluxes. As this flame has a possible heat of over 3000 deg. C, it 
can be toned down to any desired intensity by the use of air in 
some excess, though at lower temperature it will be increasingly 
oxidizing. 

Similarly, two different metals may be welded, provided their 
melting points are not more than 500 deg. Cent, apart and pro- 
vided they win form an alloy. Metals of widely separated melt- 
ing points will also weld, but the joint may be uncertain. Metals 
that will not alloy, as iron and zinc, make a poor weld. If one 
metal is crystalline and the other not, the weld will be poor, as with 



lOO 



WELDING 



steel and wrought iron. But in contradiction to this general state- 
ment, Cobleigh^ mentions a case where pieces of steel and copper 
were welded on a piece of cast iron. It looks as though skilled 
labor will soon be able to weld almost any metals or alloys that 
will melt. 

Pressuip Uegulating 
Valves 




Fig. 45. — Diagram of high pressure oxy-acetyiene system, using storage tanks. 

There appear to be no limits to the sizes of work this flame 
can weld. Plates of No. 20 gauge can be butt-welded, while cast 
iron 14 inches thick has been joined. Large work is commonly 
chamfered or beveled at about 45 deg. angle to ensure equal 

melting. When plates are butt- 
welded, the Linde Air Products 
Company^ recommends spread- 
L / /// (I ing the far ends of the plates 2 1/2 



2iH L 




Weld begins here 



Fig. 46. — Showing adjustment of 
plates for welding. 



Fig. 47. — Correct bevels for 
strong weld. 



per cent, of their length, as shown in figure 46. This, because 
the cooling and shrinking of the metal at the weld constantly 
draws the plates together. The strongest weld can be obtained by 
beveling both edges and welding both sides of the plate (Fig. 47). 

' Iron Age, Jan. 7, 1909. 
* Catalog C, 



HOW TO WELD 



lOI 



Although you are sure you have the correct mixture in your 
flame, examine your work from time to time. If the metal hard- 
ens with a spongy or scaly structure, it is burnt and you have 
too much oxygen. 

Always add about one-third thickness of metal to the weld to 
gain an equal strength. If it is necessary to machine down the 
joint to unit thickness, you need not count on more than 75 per 
cent, strength for that joint, though it may run as high as 95 
per cent. 

As with all melt-welds, the oxy-acetylene weld is benefited by 
annealing and the elasticity partly restored. 



S 30 

a 

g 
& 

oj 20 
a 

•g 15 

a 
'Z 10 

a 





















/ 
















^^y 


/^ 










i/ 




> 


>f 


^ 










"■^ 


/ 


.1'^ 




















Qjy 














/ 


^ 


^^ 
















[^ 


















-'■'''^ 



















3 4 5 6 7 

Thicknesa in mm. 



10 



Fig. 48. — Diagram of comparative welding with gas and acetylene (L. L. Bernier). 



Adaptability. — As already stated, this process is essentially 
a repair welding process. We have a very hot flame which we can 
adjust easily along a large range of sizes. The flame can be 
turned on or off at will and can be carried into any corner of the 
work. The flame is practically a hand tool. For this reason the 
several firms promoting this process are selling easily portable 
apparatus for use in machine shops, shipyards, automobile 
repair stations, and manufactories where repair work is daily 
necessary. The Fore Shipbuilding Company, the Newport 
News Shipbuilding Company, the Pullman Car Company, 
National Tube Company, United States Navy Department, and 



I02 WELDING 

many of the big machine shops of the country are using this 
process for both repair and stock welding. 

Chemical and metallurgical laboratories can use the flame to 
advantage to get very high local heats. It is suggested that the 
flame may be adapted to assay work where the rock is very 
refractory. The cost and time needed to get a high heat in an 
assay furnace is often considerable. With this flame the expen- 
sive and fragile muflle might often be dispensed with. 

The oxy-acetylene flame is now being used to weld steel tubes 
for bicycles, automobile frames, steel tanks and cylinders for 
carbonic acid, etc., angle iron, etc. Quite a bit has been written 
about the probability of acetylene-welded boilers displacing riv- 
eted boilers. Gas-welded boilers have been made, but as yet 
welded boilers are not recognized as safe, though there is no 
doubt they can be made so. Figures 50 to 57 show different 
kinds of repair and job work done by this process. 

In the hands of skilled workmen the oxy-acetylene flame is a 
safe tool for repairing such ticklish work as boiler plates, steel 
containing-cylinders, steel tubing, etc. But on the other hand, 
tests of welds have sometimes shown that the metal was either 
fatally burnt or carbonized. It would be the height of folly to 
allow a green hand to repair a boiler with this flame. In France 
an eight months' apprenticeship is required before the work- 
man is allowed to touch repair work. It is doubtful if 
acetylene welding will replace riveting for boilers or structural 
iron and steel where the strains are tensional. A good weld 
is much stronger and also quite a bit cheaper than a single- 
or even a double-riveted joint. But a riveted joint is of a 
definite known strength, and a weld may be porous and brittle 
under a good, smooth surface, and may be less than 25 per cent, 
strength. 

Typical Welds and Repairs. — The follow^ing instances 
of boiler repair are given by L. L. Bernier, in his "Autogenous 
Welding of Metals": 

"Repairing Cracks Steamer 'Eugene Pereire' of the French 
Line: 

"The boiler furnaces of the mail steamer Eugene Pereire of 
the French Line had numerous horizontal cracks above the 



HOW TO WELD 



103 



grate bars. There were about 100 of these, and in two of the 
furnaces they extended from end to end of the corrugations. 

" It had been attempted to stop the worst of these by plugging; 




Fig. 49. — Repairing with the oxy-acetylene torch (Davis-Bournonville Company) 

but it would have been necessary to renew several furnaces, 
which would have detained the steamer for two months and 
caused great expense. All the cracks were wedged open with 





Fig. 50. 

Fig. 50. — High-pressure tank for U. S. Navy. Ends and seams welded and 
3/4" flange welded to end. Material 1/2 inch thick, size 36 x 30 3/4 inches. 
Tested to 250 lbs. 

Fig. 51. — Steel tubes welded to shell. 

chisels and welded; all repaired parts were annealed with burners. 
In two spots where there were several adjoining cracks, a part of 
the furnace was cut out and replaced by a welded piece. No 



I04 



WELDING 



leak was observed at any of the loo places so repaired at the hydro- 
static or steam tests. 

" Only the sweating of a few drops, caused by trifling lamina- 
tions, were discovered, and a little calking restored the water- 
tightness at such spots. The work lasted three weeks and cost 
$300. From the month of March of that year the steamer 
has been on the Algiers voyage, which is very trying for boilers 




Fig. 52. — Galvanized tank witn oxy-acetylene welded end piece (heat expansion 
would shear rivets). 



on account of its shortness, the fires being banked and boiler 
temperatures changed so frequently. No trouble has been ex- 
perienced with any of the welded parts." 

" Repairing Corroded Parts on the ' Cholon' : 

" Oxy-acetylene welding may be used to add metal directly to 
the surfaces of plates, to repair corroded spots, such as are fre- 
quently found in various parts of boilers. The flame of the 
blowpipe is directed upon the plate, and when the latter begins 



HOW TO WELD 



loS 



to melt the workman presents to the flame a bar of soft steel 
about 7 by 7, which melts and fixes itself in drops on the corroded 
surface. 

" The repairs of the Marsa, already referred to, give a sample 
of the value of the welding process, but the work performed 
on the Cholon, of the Compagnie des Chargeurs Reunis, from 
August 20 to September 20, 1906, presents a still more striking 
case. 




Fig. 53. — Welded cylinder. Oxy-acetylene process. 



"The eighteen corrugated furnaces of this steamer were 
badly eaten away on the surface. There was corrosion on each 
side and for some distance above the grate bars. 

"The work was difficult to perform, as the workmen were 
compelled to be inside of the boilers; and were inconvenienced 
by the heat of the blowpipe flame; and the places to be welded 
were lower than the workmen's footing; 10,000 cubic feet of 
dissolved acetylene and as much of oxygen were used; about 200 
pounds of steel were used to cover the corrosions and restore 
the plates to their original thickness. This work, at a total 



io6 



WELDING 



cost of $2,400, avoided the replacing of eighteen furnaces, as 
originally ordered by the government inspectors." 

Acetylene Welding versus Riveting. — The approximate 
strength of single-riveted boiler plate is 55 per cent.; of double- 
riveted, 70 per cent. L. L. Bernier, in the Boiler Maker, gives 
the ratio of cost of acetylene welding with a generator, compared 




Fig. 54. — Top section of broken crank, case with broken arms. 



with double riveting, as seven to twelve. The cost of triple 
riveting is not given, but it would still further increase the discrep- 
ancy. Besides being cheaper, the acetylene-weld is absolutely 
leak proof, a great advantage over a riveted joint. 

On the other hand, an apparently sound acetylene-weld may 
have a tensile strength of 25 per cent, instead of 95, and may be 
crystalline and brittle; whereas the riveted joint is of certain 



HOW TO WELD 



107 



Strength. In the present state of the art it would be a mistake 
to advocate the acetylene-welding of boilers of any size, though for 
small containers and tubes that can be rolled and annealed the 
riveted and brazed joint is being rapidly superseded by the 
acetylene-weld. But oxy-acetylene repair welds are now fre- 
quently made on cracked and corroded boilers. Cracks are 




Fig. 55. — Engine crank case with welded arms. 

first laid open by a partial heating, until their full extent is 
known. Then they are welded by the flame and a melt bar, 
working up from the bottom of the crack. Where the plate is 
full of cracks or is corroded deeply, a section of the plate is cut 
out with a cutting flame and a fresh plate patch is welded in. 
Boiler repairing requires very careful preheating, hammering of 



io8 



AVELDING 



the weld and subsequent annealing of the plate surrounding 
the weld. 

Repairing Defective Castings. — One of the important 
possibilities of this process is in the repairing of defective castings 
fresh from the foundry. Even in the most careful foundry prac- 
tice the scrap heap is always a very expensive mountain to the 
foundry man. If he can keep down the heap he can increase his 
profits. With the oxy-acetylene flame all kinds of defects of 




Fig. 56. — Welded aluminum engine bed. 

castings can be repaired. Broken pieces can be put together an 
imperfect pieces built up and repaired. As with other repair 
work, a preheating torch or furnace would be needed for pieces 
of any size, even though they were of low-carbon steel. After 
the acetylene flame had done its work, an annealing furnace 
would be necessary. Both the oxy-acetylene process and the 
thermit process (see page 121) offer a solution for the economical 
reduction of the scrap heap. 

But there is one serious limitation to the possibility of using 
the oxy-acetylene flame or thermit to repair a new casting. Such 



HOW TO WELD 



109 



a casting cannot honestly be called new. The repair may make 
it stronger than a perfect piece, but the fact remains that it is a 
repaired piece. The foundryman may or may not tell his cus- 
tomer what he is selling him, according to his standard of honesty. 
It may be difficult to convince that customer that he is getting a 
first-class article and should pay full price for it. Many cus- 
tomers would not accept it under any sort of guarantee. Again, it 
might be equally damaging to the foundryman if it became known 
that he sold as perfect castings which had to be repaired, if he did 




Fig. 57. — Welded auto frame. Weld is at the white line near the base of the steering 

handle. 

so without telling the customer. Again, it is poor practice for 
the printer, the potter, the foundryman, etc., to accept knock- 
down, prices for a doubtful product, and so admit its inferiority. 

The fact remains that this flame offers a fairly cheap way of 
redeeming defective castings. The founder must use his judg- 
ment in employing it. 

How to Cut Metals. — Besides its use in melting metals 
for welding, it has recently been found that the oxy-acetylene 
flame will cut through metals. The importance of this discovery 
is not yet realized, Wrought-iron and steel plate can be cut 
through as fast as a carpenter can tear through scantling with a 



no WELDING 

rip-saw; cast iron not so readily. Other metals and alloys, 
such as aluminum, brass, etc., can also be cut. Jottrand is 
credited with this discovery. 

Cutting is effected by both the melting and the burning of the 
metal. In the case of iron, the ordinary flame heats it to bright 
heat, when an extra oxygen cock is turned on. Iron burns with 
evolution of great heat in the presence of oxygen. At the same 
time this heat is partly transmitted to the iron in front of the jet, 
while the jet blows out the iron oxid and molten metal wherever 
it strikes. When the cutting flame is at its best it entirely oxi- 
dizes the iron, blowing out a clean narrow cut. Cutting is a 
spectacular process, due to the shower of slag sparks that fall 
from the cut. 

While the cutting may be done with the oxygen flame alone, 
after the iron is red-hot, modern practice uses a preheating torch 
to which an additional oxygen jet is attached. The torch is the 
ordinary medium- or low-pressure torch, while the oxygen jet is 
above 125 pounds. Several firms are selling such torches (see 
Fig. 36). 

The torch is first adjusted to a welding flame, while the cock 
of the oxygen jet is closed. The operator points the flame at 
the edge of the metal to be cut. As soon as bright red heat is 

|| 5 ft. length \ 1 1/ ^ ' 

r '^■" % 

Fig. 58. — Iron girder cut by oxy-acetylene flame. 

reached, he moves the flame inward about half an inch and turns 
on the full oxygen jet which strikes the edge just heated. Mean- 
while the flame is heating the new part. For different thick- 
nesses of metal he can use a given oxygen tip, of which each 
torch has three. 

The rate of cutting varies with the thickness of the plate, and 
the skill of the operator. Roughly, this flame takes from 1/5 to 
i/io the time in cutting a given section of steel that two men 
working with a metal saw would take. There are several records 



HOW TO WELD III 

of 4-inch plates cut by it, while the companies claim 6 and 8 
inches for it. 

An exhibition of flame-cutting was given recently by M. 
Bournonville. During the extension work for the new New York 
subway approaches to the Williamsburg Bridge it was found 
necessary to cut through a 3/8-inch I-beam of steel, whose di- 
mensions appear in figure 58. The entire cutting took 21 1/2 
minutes. This gives the reader an idea of the efficiency of this 
process. 

This flame should be used to cut any metal that resists the 
metal saw. Should it fail to oxidize, it would melt its way through. 
An oxy-acetylene cutter should be an adjunct to every repair 
shop of any size. It would be found invaluable in cutting away 
badly wrenched metal work and in cutting and working on parts 
of any machine, such as an automobile, where a special fixture 
was to be fastened. For besides its ability to cut, this flame can 
be made to pierce rivet holes straight through one-inch steel in 
less than two minutes. 

This flame has found its way into the railroad repair shops, 
one of which uses it to cut away twisted metal on "gondola" 
coal cars. These cars are light, strong, and durable, and are 
rapidly displacing the wooden cars. But loss by wreckage is 
great and a bad wreck of gondolas is a very difficult thing to 
handle. The cars are often shapeless masses caught together by 
the force of the impact, and difficult to separate. It has some- 
times been necessary to clear the track with dynamite. Two 
storage tanks and several burners carried on the wrecking train 
would be of great assistance in such a wreck. 

Every auto repair shop of any size will probably have one of 
these oxy-acetylene outfits in a few years. The same may be said 
of ordinary machine shops, car shops, boiler shops, etc. 

A table of cutting costs has been worked out by the Davis- 
Bournonville Company, which is here appended. Oxygen is 
reckoned at three cents a foot, acetylene at one cent, and labor at 
thirty cents an hour. 



112 



WELDING 









Approximate 


Cost of Cutting Steel 








a 

•9 M 

£ .5 

u 


C 

■3 d 
^ a 


1° 




(U 
(U 

lU 


(U 
(U 

&. c 

It 

<D >, 

bo o 
n ^^, 

'S ° 
o 


° bO 

si 

£ S 




0) -t-» 

s g 
i s 


u 

«— 1 U 


1- 
t. 3 


3 



2 
J 


I 

2 
2 


4 
4 
5 


up to i" 

i" to li" 
I J" up 


12 
12 
l8 


23 


6o 

75 
95 


14 to 1 8 lbs. 
14 to 1 8 lbs. 

I 8 to 2 2 lbs. 


125 lbs. 
I2S to 150 
ISO to 175 


60 

so 
40 


■ 30 

• 30 

• 30 


2.68 
313 

4.02 


.0447 
.0627 
.1005 



Costs. — It is, of course, impossible to give costs in an empirical 
way. In the first place, improved methods of generating the two 
gases are still being advanced, as well as improved apparatus for 
production and storage. The prices of raw material fluctuate, and 
the cost of labor is increasing irregularly. But most serious, no two 
men are likely to use the same amount of gas nor take the same time 
for a specific job; nor would one workman be apt to repeat his 
performance. It at once appears, that outside of catalog prices 
for apparatus, cost estimating is as difficult as in the printing trade. 

I have given cost data at several points which must be taken 
with a little salt. Before purchasing oxy-acetylene plants, it 
would always be in order to get estimates and statements from the 
several firms handling this line; these should advise the kind of 
outfit for the work at hand. 

The table of costs worked out by the Davis-Bournonville 
Company is appended. 

Approximate Cost of Oxy-acetylene Welding 

Oxygen at 3 cents, acetylene at i cent per cubic foot; labor 30 cents per hour. 



B 


c tJ 


ption 
ylene 
our 


umption 
oxygen 
r hour 


3 0^ 

£ -a S 


U 

3 
*J 
Hi ^ 




•^ fc; 





u 


G 


•3 B 


St 


^ S y 


a a 




<1 1- 


■s a 


a 


^ ° 




§•0 ^ 



s.s 

a, 


.H S 

(U 


g a 


g- 


U .hi 


I 


■rV to j\ 


2.8 feet 


3.6 feet 


8 to 10 n 


3S. 50 feet 


$0.30 


• 436 


.0087 


2 


T^. to 3^. 


4.5 " 


5-7 " 


I to 12 


30 


0.30 


.516 


.0172 


3 


3% to J 


7.5 " 


9-7 " 


12 to 14 


25 " 


0.30 


.666 


.0266 


4 


k to i 


11-7 " 


15- " 


14 to 18 


16 ■' 


0.30 


.867 


■054 


5 


i to ^s 


18. 


23- " 


18 to 2 2 


10 " 


0.30 


1. 17 


.117 


6 


A to ^\ 


25- 


32. " 


20 to 25 


7 " 


0.30 


I-5I 


.216 


7 


t\ to i 


32s " 


41-5 " 


2 2 to 27 


5 " 


0.30 


1.87 


.374 


8 


i upward 


48.S " 


62. " 


24 to 30 






2.64 





HOW TO WELD 



113 



The following table ^ is intended to show the costs and effi- 
ciency of the three principal welding flames. Costs are figured 
on the basis of generator acetylene one cent a foot; compressed 
acetylene, two and one-half cents; oxygen, three cents; hydrogen, 
one cent; coal gas, one and one-quarter cents. I have reduced 
the estimated temperatures to reasonable limits. 





Oxy-acetylene 


Oxy-hydro- 


Oxy-coal 




mixture 


gen mixture 


gas mixture 


Number of B. T. U. obtained 








by complete combustion of 








one cubic foot of gas 


1570 


290 


616 


Temperature (Fahr.) obtained 








by combustion of the mix- 








ture (approx.) 


3000° C. 


2000° C. 


1700° C. 


Cubic feet of oxygen required 








to burn one cubic foot of gas 








to obtain the best welding 








flame (from practical tests 








made) 


1.30^ 1.70^ 


0.25 


0.67 


Cubic feet of oxygen required 








to obtain 1000 B. T. U. 








with a welding flame 


0.765 ^ 1. 00^ 


0.86 


1.09 


Cubic feet of heat-producing 








gas required to obtain 1000 








B. T. U. with a welding 








flame 


0.59 


3-44 


1.63 




■ 2.892 3.593 (ggjj. 


Cost of 1000 B. T. U. (cents) 


erator acetylene) 
3.78 2 4.393 (dis- 


5-92 


4.20 










solved acetylene) 







Chemistry and Thermics. — A definite formula should not be 
laid down for the oxy-acetylene flame as used. This for the 
reason that the products of combustion vary with different pro- 
portions of the gases and in different parts of the flame. Lewes* 

' Bulletin Technologique, Sept., 1907. 
^Medium-pressure torch used. 
^ Low-pressure torch used. 
* "Acetylene," Vivian Lewes, 1900, d. 120. 
8 



114 WELDING 

gives the probable maximum of the flame as lying between 3100 
deg. Cent, and 4000 deg. Cent. This forbids the formula of 
Davy, 

2C,H,+503 = 2H,0+4CO„ 
because water is dissociated at only 780 deg. Cent. Beltzer 
makes it 

C2H2+02 = 2CO+H2, 
while Beaupre allows less than one part monoxid in 100,000 of 
the residual gas.^ Presuming that none of the carbon forms 
monoxid, Beaupre states that oxids of nitrogen are formed in 
small quantity and ozone in very appreciable amount. Le 
Chatelier^ gives hydrogen, carbon dioxid, and monoxid as the 
principal gases from burning 7.74-17.37 parts acetylene in 100 
parts air. It is quite likely that the layer of hydrogen on the 
outer surface of the flame is partly burned to water, and partly 
dissipated. 

Theoretically, the acetylene requires about 2.5 parts of oxy- 
gen. But practice proves that this gives an oxidizing flame. 
So the proportion of i part acetylene to i . 50 oxygen is recom- 
mended. Recently M. Bournonville's experiments have shown 
that, with his torch in working order and the flame the proper 
color and shape, the proportion fell as low as i of acetylene to 
1 . 28 oxygen.^ Repeated trials confirmed these figures. How- 
ever, this seems a small matter. The flame should be decidedly 
reducing, but should not be so charged with excess acetylene 
that it will deposit carbon. 

The temperature commonly ascribed to the oxy-acetylene 
flame is 3500 deg. Cent. Acetylene is composed of 92.3 parts 
carbon and 7 . 7 hydrogen, according to its symbol. Its tempera- 
ture of dissociation is 780 deg. Cent., according to Lewes ;^ on 
burning, its heat value is 310,500 cal., according to Thomsen.^ 
This great heat need not all be attributed to the burning of 
nascent carbon, for the gas is endothermic, requiring 47,700 cal. 
for its formation." 

^ Comptes rendu., iqo6, 142, 165-6. 

^ Comptes rathi., 121, 1144. 

^ Special information. 

* "Acetylene," Vivian Lewes, igoo. 

^ Thermochcm. Unters., 4, 74. 

® Roscoe and Schorlemmer, Vol. I, p. 770. "Treatise on Chemistry." 



HOW TO WELD II5 

Le Chatelier^ gives formulas of reaction and temperatures for 
three different mixtures of acetylene with air, and shows that a 
minimum of air produces carbon dioxid and water; and an excess 
of air, carbon monoxid and hydrogen. In any case, the flame 
if properly handled is reducing beyond the blue cone, which should 
never be allowed to more than touch the work in hand. Such 
hydrogen as remains unburned in the flame is claimed to form 
a protecting envelope. 

Testing. — It is natural to expect that a unit cross-section of 
an oxy-acetylene welding will not be of equal strength with the 
metal before welding. The metal has been melted, perhaps 
oxidized or carbonized slightly, and has cooled quickly. If the 
weld is not pounded or worked while cooling, the chances are 
that the metal has crystallized and is brittle. The average oxy- 
acetylene weld is more brittle than the metal itself, and has from 
60 to 95 per cent, of the tensile strength. To make a weld as 
strong as the unwelded metal, an upset or extra thickness of metal 
must be added to the weld. Some writers make the ridiculous 
statement that the weld is even stronger than the original metal. 
This is only possible when a large joint is made. And in any 
event the elasticity is much reduced even when the joint has 
been hammered or pressed. 

But for its purpose, when carefully made, the acetylene weld 
is strong enough and compares favorably with welds made by 
other processes. Tubing, automobile frames, boiler patches, and 
miscellaneous joints which have successfully withstood the excess- 
ive shocks, stresses, or pressures demanded of them, all attest 
to the ability of the acetylene welder to do good work. 

THE OXY-HYDROGEN PROCESS 

General. — The oxy-hydrogen flame is the first, historically, 
of the high-temperature flames. It was used long before the 
discovery of industrial electrolysis of water or the production of 
oxygen by liquid-air process. The first flames were fed with 
oxygen generated from potassium chlorate and manganese dioxid 
or from the decomposition of sodium and potassium peroxids 

^ Comptes rendu, 121, 1144. 



1 1 6 WELDING 

with water or similar methods, and with hydrogen from zinc and 
hydrochloric acid or similar methods. Both the hydrogen and 
the oxygen can be used independently for the following combi- 
nations, the hottest first: 

1. Oxy-hydrogen. 

2. Oxygen-coal gas. 

3. Air-hydrogen. 

Apparatus. — The first efficient apparatus was devised by 
Newman,^ who used pure oxy-hydrogen (detonating gas) under 
2 or 3 atmospheres' pressure. The burner was a glass tube 
about 4 inches long, of i /80-inch bore. The flame was kept at 
the tip by reason of the pressure and the narrow bore. In 
1847, Robert Hare, of Philadelphia, fused 2 pounds of platinum 
with a blowpipe of his own invention. He also used detonating 
gas; and as a safety device, to prevent back-fire explosion, a handle 
packed tight with copper rods, through which the gas was forced 
to the tip. This acted on the principle of the Davy lamp. In 
1859 Deville and Debray revived this flame for platinum welding, 
and since then it has been employed in working that metal and 
also, sometimes, for gold and silver. 

- At the present time the oxy-hydrogen flame is much used in 
laboratories for production of high heat and to a limited extent 
in repair and boiler shops. It has long been the preferred method 
for sealing lead chambers for sulphuric acid manufacture by the 
contact process. Before the advent of the electric arc, bright 
light was obtained by heating a chunk of lime in this flame. This 
once widely advertised light is almost unknown at present. Be- 
fore industrial oxygen and hydrogen were made by electrolysis of 
water, this flame was quite expensive, and recently it has been 
crowded severely by the oxy-acetylene process. But in platinum 
welding, lead soldering, and laboratory research it holds its own. 
Detonating gas is made by the decomposition of water with- 
out separating the resultant gases. It can be used for soldering 
and welding, provided the burner is protected from back-fire, by 
passing the gas through a safety chamber filled with fine porous 
material or guarded by a water valve. Detonating gas is com- 
paratively cheap, though the railroads often object to handling it. 

' Encyclopedia Britannica, Vol. XVIII, p. 105. 



HOW TO WELD 



117 



Separate oxygen and hydrogen are to be preferred on account of 
safety. 

The outfit consists of tanks of the gases, tubes, and a burner 
(see Fig. 59), To prevent one gas from flowing into the other 
gas supply tank, if the pressure of the second gas should 
fail, each leading tube is provided with a safety water valve. The 
burner is a tube in a tube: the inner tube carrying oxygen, the 




Hydrogen, 
j^ Inlet 

Fig. 59. — Oxy-hydrogen blowpipe. 

surrounding tube hydrogen. Both have cocks. The hydrogen 
is first turned on and lighted; then turn on the oxygen. This 
burner is also suited for oxygen-coal gas. 

Figure 60 shows the air-hydrogen torch; the hydrogen is 
injected at the handle and draws in air through holes in the tip. 
The amount of air is regulated by a ring. This burner resembles 
the Bunsen burner, and is used for small work, where great heat 




Fig. 60. — Hydrogen-air blowpipe. 

is not needed. The hydrogen may be produced by the zinc-acid 
process. 

M. U. Schoop,^ the welding expert, recommends the burner 
shown in figure 61 for large-scale work. The torch has two 
chambers. The first is filled with oxygen. The hydrogen tube 
passes through this chamber into the second. The injected 

' Electrochemical and Metallurgical Industry, July, 1905. 



Il8 WELDING 

hydrogen draws oxygen from the first chamber into the second, 
where they mix before coming out at the nozzle. This torch is 
hable to back-fire, but it gives a perfect combustion and prevents 
■ free oxygen in the flame. 

The air-hydrogen process is apparently cheaper, but when it 
is considered that much less heat is evolved and that three hours' 
time are needed to one hour for oxy-hydrogen, it turns out to be 
dearer. Schoop claims that it is more dangerous than oxy- 
hydrogen. It is the preferred flame for "lead burning," as 
the sealing of lead seams is called. C. H. Fay^ has explained the 




Hydrogen 
Inlet 

Fig. 6i. — Oxy-hydrogen burner allowing perfect mixing of the gases. 

apparatus and process in great detail. He used apparatus of the 
Kirkwood Sl Herr Hydrogen Machine Company, of Chicago. 
It included: an air gasometer; a hydrogen-generating apparatus, 
using zinc and sulphuric acid ; and a regular burner with two cocks. 
If the hydrogen was used under pressure up to 30 pounds, the air 
gasometer could be done away with, and air introduced by in- 
jection instead. 

The Flame. — Oxygen and hydrogen for combustion are mixed 
in a long-shanked burner at the lower end of the handle. They 
burn at the tip with a pale blue, almost colorless flame. The 
theoretical formula of combustion is 

2H2+02 = 2H20. 

Though these gases wifl unite as low as 155 deg. Cent.,^ the 
action is slow. Explosive ignition of mixtures of the gases in 
different proportions occurs at an average temperature of 825 deg. 
Cent. Richards^ gives the temperature of the hottest part of the 
flame as 3 191 deg. Cent., and of the air-hydrogen flame as 

' "Lead Burning," 1905. 

^Electrochemical and Metallurgical Industry, May, 1Q05. 

^ Roscoe and Schorlemmer, Vol. I, p. 287, "Treatise'on Chemistry." 




HOW TO WELD II9 

2010* deg. Cent. Bunsen's experiments gave a maximum of 
2844 deg. Cent. The former temperature, of course, is not to be 
found throughout the flame, if at all. The actual temperature 
is probably not much above 2000 deg. Cent, under working con- 
ditions, and while this is above the fusion point of most of the 
metals, it is none too high when conduction is reckoned on. The 
heating value of the hydrogen flame is much less than the acetylene, 
being 67,940 calories. 

Practice.- — In using the oxy-hydrogen flame it is necessary 
to use an excess of hydrogen over the theoretical amount of two 
volumes to one of oxygen. 
Otherwise there is danger 
of oxidizing the metal sur- 
face with hot oxygen. 
Platinum is the exception. 
Tliis metal absorbs hydro- 
gen and swells up. When 

cooling, it occludes the gas ^^^- 62.— Lap welding lead sheets with 

" ° air-hydrogen Hame. 

and becomes rough and 

pocked. One writer^ recommends 4 to 5 volumes of hydrogen 
to I of oxygen for ordinary welding. This is so in the case 
of iron, copper, aluminium, and other oxidizable metals, when 
the unmixed-gas type of burner is used. But no such excess is 
necessary where the gases are mixed before ignition. 

In lighting the oxy-hydrogen burner, turn on two-thirds of the 
hydrogen first and light it, then turn on oxygen until you have 
a pale blue conical flame. Then turn the hydrogen on full. 
If the burner is of the type shown in figure 61, do not light 
for at least ten seconds; and turn the oxygen off first when 
extinguishing. 

The air-hydrogen flame, being cooler, must be larger. Hydro- 
gen is turned on and lighted first. The flame will be about 3 
inches long, pale red, and will burn unsteadily. Now turn on air 
until the flame shortens to 2 inches and has a fixed, pale blue 
cone. If you are using an injector air-burner, you regulate the 
air by turning the air ring. 

In using either flame do not bring the end of the cone of 

' Electrochemical and Metallurgical Industry, May, 1909. 



I20 WELDING 

oxygen against the work in hand. If you do, you are liable to 
burn your metal. 

The operator is advised to use a flame of such size that it will 
not melt the metal at once. Slow melting will make a better 
job, and the metal will not be so apt to run away from the joint 
before he is prepared for it. Operators commonly weld a drop 
at a time as shown in figure 62. They then go back over the 
seam a second time to smooth off the surface. 

Different metals require different treatment. There are little 
points in the handling of this flame that the operator will have 
to work out for himself. Like any highly efficient tool, it requires 
a skilled workman. 

"The time^ for welding i meter of sheet iron 3 mm. in 
thickness is about 15 minutes, while for welding i meter of sheet 
metal of o. 5 mm. thickness, it is from 4 to 6 minutes." 

' Electrochemical and Metallurgical Industry, F. C. Perkins, May, 1906. 



Part IV— Thermit 



THE THERMIT PROCESS 

General. — One of the most recent and successful methods of 
welding is called the Thermit Process. It was invented by Dr. 
Goldschmidt, of Essen, Germany, and is exploited by the com- 
pany bearing his name. In this process a mixture of aluminum 
and oxid of iron is ignited. The aluminum reduces the iron from 
its oxid, and evolves an intense heat, about 2500 deg. Cent., or 
twice the temperature of molten steel. This molten steel, called 
thermit steel, is then poured around the metal to be welded and 
forms a melt-joint that is very strong when cold. Its present 
application is entirely in repairs of large metal pieces and in 
making continuous welded railroad track. It is used in repair 
shops for mending car axles, auto and electric motor cases, broken 
and defective castings, broken parts of reciprocating engines, 
broken rudder-posts, skegs, and sternposts of ships, and for repair 
work in general along this line. Special thermit mixtures are being 
advocated for toning up the melted steel in the ladle in foundry 
practice, for preventing "piping" of ingots; and the company is 
using the strong reducing property of aluminum in reducing a 
number of the less used metals, such as tungsten, chromium, and 
boron, to a pure metallic state. 

Thermit is first of all a welding process. Its good and weak 
points may be summed up thus: 

1. Simplicity of the apparatus. 

2. No special skill needed to do the work. 

3. Possibility of repairing breaks difficult of access and of 
repairing parts in situ that would otherwise have to be taken out. 

4. Possiblity of intense local heating of large parts. 

5. Time and money saved in most repair work. 

6. Possibility of varying the chemical composition of thermit 
steel so that its properties may be varied. 

121 



122 • WELDING 

7. It is at present limited to rail welding and repair work. 

8. Only iron and steel can be welded. 

9. The cost, though much lower than the forge method of 
welding, is still often prohibitive. 

The process is used by many of the leading railroads, shipyards, 
and machine shops of all of these countries, both for repair work 
and for special jointing, such as that of the third rail of the Paris 
subway. At present Dr. Goldschmidt is trying to produce chem- 
ically pure metals on a commercial scale. He has met with 
success in reducing metallic manganese, chromium, tungsten, 
vanadium, molybdinum, boron, etc., from their ores and oxids. 
This new field in metallurgy, now called aluminothermics, seems 
to promise as many new and interesting possibilities on its 
horizon as did the experiments of Moissan with his electric 
furnace. 

The fundamental idea beneath thermit has been in the minds 
of metallurgists for at least a half-century. In the year 1869, a 
Mr. Budd^ describes a process for reducing the alloyed silicon in 
pig iron. His idea was to burn it out with hematite ore, the 
formula being: 

3Si+2Fe203 = 4Fe +38103. 

He made a paste of hematite and smeared it over the bottoms 
of the pig molds. The molten iron, which appears to have been 
much too high in silicon, was run into the molds, and immediately 
the silicon began to burn out of the iron, first taking up the oxygen 
of the hematite mud on the bottom of the mold, and then uniting 
with some of the iron and coming to the top as a silicate-of-iron 
slag. Most of the iron reduced from the hematite added itself 
to the pig. Like the Goldschmidt method, this was the reduction 
of one metal by the transfer of its oxygen to another metal. 

The fact that aluminum has the greatest affinity for oxygen 
has long suggested it as a final reducing agent. And its steady fall 
in price since its discovery by Woehler in 1857 finally brought it, 
about 1895, within range of the market. Woehler himself tried 
to smelt chromium from its chlorid by ignition with metallic 

' Transactions of the Iron and Steel Institute, 1869; "On a New Process for 
Removing Silicon from Pig Iron." 



THE THERMIT PROCESS 1 23 

aluminum. After an explosively violent reaction, he found he 
had an alloy of chromium with aluminum. 

A number of later attempts were made to use aluminum as an 
agent for reducing the rare metals from their oxids. Yet, though 
it had an intense affinity for oxygen, the combustion was hard 
to start, and when started was hard to control. Experi- 
menters mixed it as a powder with a metallic oxid and 
heated the mixture from the outside. Finely divided metallic 
aluminum will not burn at the temperature of molten 
cast iron. So that when the contents of the crucible began to 
react, the initial temperature was already so high that the reaction 
was an explosion. Dr. Goldschmidt overcame this by setting 
off the cold powder with a fuse of barium peroxid, BaO, which 
in turn was set off by a storm match. A charge of several pounds 
was found to burn in less than 30 seconds, and the temperature of 
the mass rose to an approximate 2500 deg. Cent. Larger quanti- 
ties, though starting to burn from a cold and coarsely powdered 
sand, often boiled over. A premixture of cold steel turnings 
remedied this. The result of the burning was an intensely hot 
iron whose composition could be varied at will. 

The commercial value of this invention is obvious. There 
are many processes and many emergencies where a very hot 
molten iron is invaluable, yet where it is difficult and expensive 
to get this heat by any known means. Take the case of a broken 
casting of some large machine that would in the ordinary course 
of repair have to be taken apart and shipped to the nearest forge 
to be welded. If, however, a definite quantity of iron, heated to 
twice its melting point, can be made on the spot, it can be poured 
around this break without dismantling the machine. It will 
then form a welded union, much as though one were to put the 
butts of two candles together and pour hot tallow over the joint. 
The tallow would melt into the candles before it itself cooled, 
and join the two with a homogeneous substance. 

In order that the mechanical aspect of the thermit weld may 
be clear to the reader, a simple case of rail welding will be out- 
lined. After which the appliances used in the process will be 
described in detail. 

Apparatus and Rail Welding. — Suppose a case of two rails 



124 WELDING 

abutting which are to be welded together. It is a railway cross- 
ing where heavy trains pound. The weld must be at least as 
strong as the rail. It must be so made as not to interfere with the 
travel of the wheels by coming up over the head of the rail. First 
of all, the rail ends must be cleaned of oxid and grease with a sand 
blast or emery-paper or hydrochloric acid. Next, the rail ends are 
heated to a dull red heat with a kerosene or, preferably, a gasoline 
torch. This merely assists the hot thermit metal and prevents a 
premature chilling of the thermit when it is poured in the mold. 
Two clay molds are next clamped on either side of the junction. 
The shape of the interior of these molds is, of course, determined 
by the shape of the collar which is intended to be cast. In this 



Fig. 63. — Rails before welding. Fig. 64. — Welded rail, showing 

thermit-steel shoulder. 



case, as shown in figure 64, the collar should extend 2 inches 
over each rail end. It shall be twice as thick as the shank of the 
rail and also the base of the rail. It shall stop short of the rail 
heads, which shall remain free. The mold is constructed so as 
to allow the molten metal to be introduced from the bottom, as 
shown in the figure. After coming in from the runner, at the bot- 
tom, the slag and excess steel overflow into the riser. 

We have then two rails enclosed in a mold whose capacity, 
over the rails themselves, is known. To produce enough thermit 
steel to well fill this mold and to allow as much more to fill the 
runner and the riser, take eighteen times as many ounces of thermit 
powder as there are cubic inches of surplus space in the mold. 

The above amount is arrived at as follows: One cubic inch 
of steel weighs 4 1/2 ounces. Four and one-half ounces steel is 
produced by twice as much thermit powder by weight, or nine 
times. And as the runner and riser take as much fluid as the 
inside of the mold, we multiply again by 2 and get eighteen. 

When a wax collar is first built on the joint, the amount of 
thermit should be thirty-two times the weight of the wax used. 
The weight of the wax used is found by subtracting the weight of 



THE THERMIT PROCESS 1 25 

the piece of wax remaining from the total weight of the original 
wax lump. 

The proper amount of thermit powder is poured into the cone 
crucible (Fig. 65), and a spoonful of barium hydroxid is heaped 
upon the thermit. The crucible is placed with its tap hole about 
4 inches above and directly over the hole of the riser in the mold. 
Set off the barium powder with a storm match and get away as 
soon as the barium is caught. The burning quickly spreads from 
the barium fuse to the thermit, and in a fraction of a minute the 
entire contents of the crucible are boiling at a temperature of 
about 2500 deg. Cent. White smoke, flames, and drops of white 
hot slag are ejected during the combustion, which is most spec- 
tacular and reminds one of the blowing of a Bessemer converter. 
In working with thermit is is well to wear smoked glasses, as the 
glare of the reaction and the hot fluid is troublesome. In about 
thirty seconds the reaction is completed, but the crucible should be 
allowed to stand for a half-minute longer to enable the slag to 
rise to the surface. It is probably for the reason that the slag 
does not have time to rise before the workman taps his crucible 
that the joints sometimes show blow holes and faulty structure. 
About a minute after lighting the fuse, the workman knocks the 
stopper out of the bottom of the crucible, and the white-hot metal 
pours out into the mould. As the stream enters the mold from 
below (Fig. 71) it heats the ends of the rails and passes on up and 
out into the riser. The last of the metal stream remains in the 
mold, and as it is very much hotter than the melting point of steel, 
it eats into the sides of the rails and knits fast on cooling. The 
joint should remain undisturbed for at least five minutes to allow 
the metal to harden. It may then be treated in a number of 
ways — either allowed to cool slowly in the mold, in which case 
the joint will be composed of soft, tough steel, or quenched in oil 
from a red heat, in which case the joint will be very hard, and per- 
haps brittle. 

While this description does not give all of the steps of rail 
welding, it will give the reader a fair idea of how all thermit 
welds are made. The apparatus used is as follows: 

The Crucible. — With the exception of butt-welding, where an 
ordinary hot crucible is used, the crucible for all thermit-welding 



126 



WELDING 



is a cone-shaped affair that taps at the bottom. It is an evolution 
of the thermit process, and is so designed that the molten iron can 
be drawn off before the slag (Fig. 65). 

It is in the shape of an inverted cone, having a rounded iron 
top which is clapped on as soon as the charge is fired to prevent 
spattering and loss of heat. The crucible is tapped through a 
hole in the bottom. It is supported on a tripod or can be slung 
from a crane or overhead arm. 

The body is of pressed steel, lined with several inches of 
magnesia. Magnesia is slightly more refractory than silica and 
it has the advantage that it will not unite so readily with the 
molten steel. Hence the steel remains basic. 



Removable Top 




Asbestos Washer 
Sand 



Head of 
{Tapping Tin 



Tap Hole 




Magnesia 
Stone 

Magnesia 
Tbimble 



Tapping EiA 



Fig. 65. — Thermit crucible with detail of lap hole. 



The tap hole is the vital part of the crucible. It must remain 
fluid-tight until tapped, and must then withstand the rush of 
molten steel under pressure. As shown in figure 65, the bottom 
of the crucible holds a large cylindrical magnesia stone which has 
been placed in position before the magnesia lining has been 
tamped in. Resting inside the stone is another conical-shaped 
magnesia stone, called the "thimble." It is also hollow, and its 
core is the channel for the molten steel. An iron tapping pin, 
having a long shank and a fiat head, is dropped into the hole in 
the thimble; its head acts as a plug to the channel. An asbestos 
washer is dropped on the head of the tapping pin, then an iron 
washer, and next an inch of silica sand is poured on the iron 
washer. This makes a plug to the crucible that is fluid-tight for 
at least a minute, long enough for the reaction to take place. 



THE THERMIT PROCESS 



127 



This plug is tapped by driving the pin up from the outside by 
hitting it with a spade. The fluid rushes out and melts the 
tapping pin as it goes. 

A new tapping pin is needed with each reaction; a new thimble 




Fig. 66. — Rail patterns. 

every eight or ten reactions; a new crucible lining every twenty to 
more reactions. 

The lining of the crucible is a mixture of tar and magnesia, 
which is tamped in between the crucible steel and an iron matrix. 
When lined, the crucible is baked at a red heat for six hours, 
when the lining becomes hard. Even such a substance as mag- 




FiG. 67. — Rail mold boxes. 

nesia melts away under the heat of the thermit reaction, and after 
several melts the interior resembles the walls of a Bessemer 
crucible. 

The Mold. — Molds for thermit work are adapted to the par- 
ticular joint to be made. For welding a number of joints of uni- 



128 WELDING 

form size the company furnishes patterns with which the operator 
can make his own molds, or else the company will furnish the 
molds themselves. Thus it will be convenient and cheap to buy 
or make special molds for continuous rail welding, pipe welding, 
rod welding (as in the case of steel rods in reinforced concrete), 
locomotive-frame welding, or in other repair work that turns up 
regularly. 

Take the case of rail welding, such as the welding together of 
a continuous third rail for the Paris, France, subway. We will 
presume the mold patterns (Fig. 66) to represent the obverse 
shape of the rail. The patterns are laid down, face upward, 



Fig. 68. — Finished rail molds. 



and covered with their respective mold boxes (Fig. 67). The 
molding material is then rammed into place, and when the box 
is level-full, the operator pricks a number of holes all the way 
through the mold to allow the escape of gases when the mold is in 
use. As soon as formed the molds are placed in a drying oven 
for six hours at a heat of 500 deg. Fahr., until they have become a 
light brown color. Do not let them burn black, as they will then 
crumble easily. The molds are generally cast inside of an iron 
retaining frame or with iron handles. 

Mold sand must be more refractory than the ordinary river 
sand, which has enough iron and alumina in its make-up to 
render it easily fusible by the hot thermit. Coarse white silica 
sand and fire clay in equal proportions is the best, price consid- 
ered. Cheap rye or wheat flour, proportion of i to 15, is the 
binder used. The sand and flour are mixed dry and then mois- 
tened to a stiff mass. Where an extra strong mold is needed, the 



THE THERMIT PROCESS 



129 



operator can mix a spoonful of turpentine to each mold portion. 
For binding material it is not advisable to use the foundryman's 
occasional expedients, such as molasses, larger amounts of 
flour, clay, pitch, etc., for two reasons: The binder is subject 
to the great heat of the molten thermit. The more binder used, 
the greater space will be left when it burns out, and the mold will 




Fig. 69. — Mold partially assembled. 

fall to pieces after two or three usings. Also, if much binder is 
used, its rapid burning will cause excessive gases which may 
burst the mold, and which are also liable to injure the composition 
of the steel joint. 

A good sand-flour mold should last for ten or more welds. 
Its life depends on the operator's skill in making and his care in 
using it. 



Riser 




Fig. 70. — Assembled thermit mold. 

For the welding of joints similar to rails, the molds used will 
vary in shape, but have the same composition. The operator 
can carve his own patterns out of wood. 

For butt-welding of pipes not exceeding a diameter of i 1/2 
inches and of solid rods not exceeding 4 square inches cross- 
9 



I30 



WELDING 



section, an iran mold is preferable because it is solid and easy to 
handle (see Fig. 75). 

For welding larger breaks, such as fractured locomotive frames, 
the fire-clay, or fire-brick, mold is recommended. In this case 
the cross-section to be welded may range from 2 by 3 to 5 by 6 



Riser. 



Pouring Gate 




^Heating Gate 

Fig. 71. — Sectional view of mold. 

inches. An iron mold would absorb the heat too rapidly. The 
thermit collar would chill prematurely, and the mold itself would 
probably crack or melt, being cast iron. While a soft sand mold 
would propably crumble. The company furnishes a hard- 
baked, fire-brick mold, which is strong and refractory, at the 
same time being a fair non-conductor (Figs. 69 and 70). 




Fig. 72. — Tapping the crucible. 

It often happens, in thermit repair work, that the fracture to be 
mended is of a peculiar shape. The operator will be at a disad- 
vantage in making his patterns, as the fracture is not only irre- 
gular, but the shape of the piece prevents measurements for a 
mold being taken. In this case the operator builds up a collar 



THE THERMIT PROCESS I3I 

of cerecine wax of the size and shape that he intends for the 
finished welded collar. He then places the piece in an iron mold 
box, and tamps it around with wet sand, at the same time insert- 
ing wooden forms for pouring gate and riser; he next turns the 
flame of a gasoline torch into a special hole in the bottom of the 
sand box. The wax melts from around the piece and runs out of 
the hole. The flame is continued until the sand is dried, 
and then the operator stops the bottom hole in the mold 
with a sand plug. As already suggested the amount of ther- 
mit powder necessary for such a mold is thirty-two times the 
amount of wax, by weight. It should take less than twenty 
minutes to place a wax collar on an ordinary break and twenty 
minutes to dry out the mold. The cost of the wax is about ten 
cents per pound, so that for mending occasional or oddly-shaped 
breaks the wax mold is the cheapest and quickest. It is used for 
welds of embossing- and stamping-press pieces, forging hammers, 
stern-posts and rudder-posts of sailing vessels, gun-carriages, 
motor cases, etc., etc. 

Practice. — It should be borne in mind that the thermit joint 
itself is a steel casting of average analysis of: 

Carbon o . 05 to o . i o 

Manganese 08 to .10 

Silicon 09 to .20 

Sulphur ^ 03 to .04 

Phosphorus 04 to .05 

Aluminium 07 to .18 

Its average tensile strength is about 30 tons per square 
inch cross-section. If the joint is good, the thermit will amalga- 
mate so closely with the metal of the welded parts that a ground 
and polished section of the joint will not show any marks of 
junction, even though the metals be of different color and struc- 
ture. Therefore, the operator has only to calculate whether he 
shall vary the chemical composition of his thermit to give his 
weld the desired strength or whether he should gain strength 
by casting a big shoulder on the joint. 

There are a number of instances where the shoulder must be 
machined off, though the weld must be as strong as the rest of the 
piece, as in the case of rails, bearings, etc. 



132 



WELDING 



Most welds permit of as large a shoulder as is needed, as 
in the case of ship stern-posts. 

To make sure that the metal of the shoulder adheres to the 
parts, the latter should be made hot before the thermit is poured. 
If the shoulder is simply a loose collar of metal around the part, 
it does not add to the strength of the weld. Where the welded 
part is subject to bending stresses, it is important that the shoul- 
der be knit to the surface of the parts welded. The company- 
recommends heating the parts to redness if possible before pouring 
the thermit. 



r 




Fig. 73. — Reproducli(jn of photograph of a weld showing "blow" holes. 

It is claimed that the air holes and shrinkage cavities, which 
thermit steel sometimes shows, are also due to insufficient heating 
(see Fig. 73). Where the parts to be welded are quite cold, it is 
probable that the thermit steel freezes as soon as it touches, caus- 
ing imperfect circulation around the joint, and hence allowing a 
faulty structure in the weld. 

Blow holes and separation planes are two of the common 
diseases of the thermit weld. Faulty mixing of the thermit 
"tonics," improper preheating, and improper pouring or tapping 
are all blamed for these defects. 

Setting the Pieces .-^Where two pieces of iron of more than 
i-inch section are to be joined, it is best to allow a 1/2 inch space 
between the abutting ends, for it is necessary that the thermit 



THE THERMIT PROCESS I33 

have free flow around the ends. It must either melt the abutting 
ends or there must be a passage between them for the thermit 
to flow. 

In the case of rails, the ends of the rails are brought close 
together, as the thermit can easily melt the ends. The same 
is also true in the case of small rods and pipe. It is important 
to keep the rails in perfect alignment while welding. 

In the case of locomotive frames where it is doubtful whether 
the thermit could melt its way into the fracture, the operator 
drills a line of 1/2-inch holes down the break; through these 
holes the thermit enters (see Fig. 85). Also in the case of anchor 
flukes, ship's stern- and rudder-posts, large castings, such as 
anvils, hydraulic hammers and presses, etc. 

In the case of locomotive frames and driving-wheel spokes 
the shrinkage of the joint on cooling will spoil the piece if not 
allowed for. The locomotive frame is jacked open from 1/8 
to 1/16 inch before the mold is placed. In the case of the driv- 
ing-rod equal expansion of the other spokes on the piece can be 
had by heating short sections of each spoke to redness until the 
weld around the broken spoke begins to set. All the spokes will 
contract together and the strain will be minimized. 

Cleaning the Pieces. — The thermit reaction consists in the 
reducing of iron oxid by aluminum. Hence it is supposed that 
the thermit steel, when molten, will clean the scale off the joint 
to be welded. So it will; but this scale will go into solution 
as iron oxid. If there is much scale on the joint, the thermit 
joint will become full of iron oxid and will be "burnt" and 
brittle. Contrary to the advise contained in the company's 
directions, I would recommend that the pieces be kept as clean 
of scale as possible. If they are heated to redness in preheating, 
of course fresh scale will be formed. But the operator should 
begin by cleaning his pieces with sand blast or sand-paper or by 
tapping. 

As with ordinary blacksmith welds, it is also important to rid 
the joint of grease by mechanical means or by scouring it with 
dilute alkali. 

Preheating. — It is necessary to heat with a torch all pieces 
about to be joined, for the reason that the molten thermit must 



134 WELDING 

meet a hot responsive surface of metal when it flows into the 
mold. If poured into a cold mold and on to a cold joint, the 
thermit may be chilled enough to make it flow slowly and im- 
perfectly. The result will be an imperfect junction, and the 
shoulder of the weld may be full of air-holes and minute cleavage 
planes from rapid cooling. Do not rely on the great heat of 
thermit, but preheat in all cases except butt-welding. 

For most work a gasoline or benzene torch is good enough. 
The flame is fairly neutral and will not form scale very fast. 

For hea.ting very large pieces, several torches are often needed. 
In shop repairing, producer gas may be used; and in this event 
the burner can be made to give a reducing flame, which will 
prevent scale from forming. 

As to temperature, the joint should be at least hot enough to 
vaporize water drops with violence. It is well to heat the joint 
to redness where it can be done. But where the pieces are large, 
they will conduct the heat away from the part where the flame 
is playing; the operator must be satisfied with a temperature 
ranging about 300 deg. Cent. 

Safe-guarding the Mold. — Bear in mind that liquid thermit 
is exceedingly fluid — as much so as warm molasses — and as it is 
much heavier, it will search diligently for all openings in the mold. 
For this reason the mold must be tight at the entering of the iron 
pieces. The operator should have at hand a bucket of luting 
clay, made of equal mixtures of fire-clay and sand, made pasty 
with a little water. 

If the molds are solid pieces, as in rail and locomotive-frame 
welding, he smears a thin layer over the surface of the molds 
where they come in contact with one another. This will make a 
fairly tight mold. 

Also he must stuff luting clay around the mold where the 
iron pieces enter, otherwise the thermit may find its way 
along the iron and spurt out. The danger of an unexpected 
squirt of thermit need not be dwelt on. 

When the mold is made of fire-clay tamped over a wax collar, 
there should be no leaks if the operator is careful. He must be 
sure that his mold is rigid and strong enough to hold the extra 
weight of the pour. 



THE THERMIT PROCESS I35 

A possible overflow of thermit and slag must be provided for. 
Large pours of thermit are always made with this in mind. If 
the pour is made in the workshop, the floor should be of sand 
and the workman should remove his tools before tapping. After 
tapping the thermit he should remove himself as quickly as 
possible. 

Amount of Thermit. — As has been stated elsewhere, there 
should be twice as much thermit steel poured for a weld as is 
necessary to fill the space between the joined pieces and to provide 
for shoulder around the joint. The first of the thermit pour 
that reaches the inside of the joint expends most of its heat in 
raising the temperature above redness. It passes up the riser, 
leaving the interior so hot that the last of the pour settles easily 
around the half-molten joint and is fluid enough to make a homo- 
geneous casting. 

The amount of the thermit powder used in a weld is eighteen 
times the unoccupied space in the mold after the joint is adjusted 
and ready to weld. The thermit is estimated in ounces, the 
space in cubic inches (page 124). This number, eighteen, 
provides twice as much thermit steel as is needed for the weld, 
the rest, as already stated, going into the riser. However, P. 
Redington^ and H. L. Des Anges- advise that three or q\ en four 
times the amount of steel is needed to get the best results. This 
may be due to imperfect preheating. 

The Reaction. — The reaction is rapid and violent. There 
is no explosion, but the crucible sends up a shower of sparks much 
like the kind of fireworks called a "flower-pot." So to prevent 
this and to conserve the heat, a loose metal top is slipped over the 
crucible as soon as the fuse is lit. 

The workman should use smoked or colored glasses to protect 
his eyes. 

The reaction takes not longer than thirty seconds. The 
crucible should not be tapped for at least ten seconds thereafter, 
because the reaction has left an intimate mixture of slag in steel 
in the crucible, and a little time is allowed for the slag to float to 
the surface.^ I believe that outside of insufficient perheating, one 

' Foundry, April, 1905. 

^ Foundry, August, 1905 

5 Ihid., R. Webb, July, 1905. 



136 WELDING 

of the common causes of failure of thermit welds is premature 
tapping. * No steel is strong if it is premeated with slag. 

After Pouring. — After pouring, you have an ordinary steel 
casting, with this exception — that the heat of the joint will be 
conducted by the body of the part much faster than is good for a 
stee-l casting. If you are welding a fractured locomotive frame, 
and you want to assure yourself that the joint will be as tough as 
the frame, you had best give the joint several hours' annealing by 
such means as are at hand. 

Annealing is not so necessary in a thermit joint as it is in the 
oxy-acetylene and other welds. Thermit steel shows a low- 
carbon content. Rapid cooling will not temper it highly. But 
no chilled steel is as tough as the annealed product. Tests in 
practice seem to show that after-heating gives an even-grained 
and tougher joint. ^ 

The results of after-heating may be attained in a lesser degree 
by keeping the mold in place until the joint is cooled. Cooling 
may take several hours with the mold on if the pieces are large. 

Nickel Addition. — Nickel thermit is an alhed substance to 
thermit proper. It is a mixture of nickel oxid and aluminum, and 
the reaction sets free the nickel in the metallic state. 

3NiO -t-2Al = 3Ni-[-AU03. 

If the operator wants a higher tensile strength without dimin- 
ishing his elastic limit, he introduces a can of nickel thermit 
into his ladle of molten iron, as already described. Or the 
nickel thermit is fired in a hand-ladle, using a small quantity, and 
pouring in the remainder of the package gradually as the reaction 
progresses. The entire contents of the hand-ladle are poured 
into the big ladle, which should be one-third full of molten iron. 
The big ladle is then poured full of iron and a can of titanium 
thermit is poled in to cause a thorough mixing of the iron and 
nickel. 

One per cent, of nickel is sufficient to increase the strength of 
ordinary iron about one-third. Two per cent, of nickel thermit 
gives a little more than i per cent, metallic nickel. 

^Foundry, Jas. F. Weber, July, 1905. 

"^Journal U.S. Artillery, Gustav Reiniger, July-August, 1907. 



THE THERMIT PROCESS 137 

Metallic nickel is also added to thermit, using 5 ounces 
nickel to each 100 pounds thermit if you wish to make a i per 
cent, alloy. 

Titanium Addition. — Titanium thermit is another "alumino- 
thermic" substance having the reaction 

3Ti02+4Al=^2Al303+3Ti. 

It is introduced into the ladle in foundry practice for the 
purpose of purifying the iron. About i per cent, is recommended. 
As its office is to reduce the sulphur and nitrogen, most of it re- 
appears in the slag. Its effect is to greatly increase the strength, 
presumably by making the metal close-grained and homogeneous. 

Butt-welding of Pipes. — One of the unique applications of 
thermit is in the butt-welding of pipes and bars. It is a very 
difficult and often impossible thing to make a strong joint of two 
gas or water pipes without cutting reverse threads on the two 
and using a sleeve union. Welding such joints by ordinary 
means is generally out of the question, because with the facilities 
ordinarily at hand, it is difficult to obtain the right welding heat, 
and almost impossible to keep the surfaces clean enough to join 
them. 

In using thermit for butt-welding, the slag of the thermit reac- 
tion is poured into the mold before the metal. It covers the iron 
surface in a thin layer that is at once chilled and adheres to the 
metal. This coating of slag serves as a distributor of the heat 
of the thermit metal to the iron, at the same time preventing direct 
contact of the thermit metal with the pipe. As soon as the oper- 
ator believes the pipe ends are plastic, he pulls them tightly 
together, and the weld is effected. 

As this is a very practical and necessary weld, it will be well to 
explain the operation and the appliances in detail. 

Suppose two I -inch abutting gas pipes are to be welded. The 
ends are first cut square and filed to smoothness, so that when the 
pipes touch their ends shall fit closely all around. Clamps are 
then fitted on the pieces, about 5 inches from the ends, and 
screwed tightly on the pipes. These clamps have sockets for 
two connecting draw screws, which are fitted in place and 



I3S 



WELDING 



tightened with pins (see Fig, 74) until the pipe ends touch. 
Brace the pipes so that they ahgn as they should and place the 
lower mold jaw under the joined ends of the pipes, so that the 
line of joining is in the middle of the mold. This mold is a 
hinged affair, ha\ing two handles, and resembles a nut-cracker 
(see Fig. 75). 



Draw Pin 



Joint 




Fig. 74. — Clamps in position. 



Draw Pin 

Pipe-welding by thermit. 



The thermit portion, about 2 pounds, is poured into a small 
cup crucible, which is lined with magnesia and operated with 
a pair of tongs. Allow the crucible to stand half a minute after 
firing, so that the slag and steel can separate. Then pour over 
the lip of the crucible so that the slag comes out first. Begin 
pouring at one end of the lip of the mold and travel to the other 
end. As the thermit slag is poured in on a cold surface of pipe, 



Pouring Gate 




Fig. 75.-^Mold for pipe- welding with thermit. 

it forms a hard shell around the metal, and the liquid which 
follows distributes its heat evenly through this shell, which is a 
poor conductor. During the pouring, the operator's assistant 
presses the handles of the mold together to keep the mold in close 
contact with the pipe. About one minute's time is allowed for 
the iron of the pipe to reach welding heat. The draw pins are 



THE THERMIT PROCESS 



139 



put in the sockets of the clamps and screwed tight. If the pipe 
ends are plastic and ready to weld, the operator can feel it by 
screwing the draw pins. The nuts on both pins are given two 
full simultaneous turns by the operator and his assistant. This 
is enough to force the pipe ends together and complete the weld. 
If the operator desires, he can force enough metal into the upset 
by giving the draw nuts another turn, to make the joint con- 
siderably stronger than the pipe itself. 

The mold is taken off at once by tapping the upper jaw loose 
with a hammer. The slag collar which adheres to the pipe is 
knocked off carefully, and the red-hot joint 
is allowed to cool. 

The draw bars and clamps which held 
the pipes together are removed as soon as 
the weld is cooled. The joint will have a 
slight upset due to the extra metal forced 
into it. This may be machined off if 
necessary. 

Tests on such a weld will give a frac- 
ture or a crease in the pipe outside of the 
line where the mold fitted. 

The foregoing weld was made on a hori- 
zontal piece of piping. For an inclined or 
vertical piece, the apparatus and process 
are the same, except that the mold will 
have its mouth placed in the side so that the thermit can be 
poured in when the mold is in place (see Fig. 76). 

For pipes or rods of different thickness or diameter, the size 
of the mold will vary, also the amount of thermit to use and the 
time it takes to raise the joint to welding heat. The manufac- 
turers supply both molds and clamps for pipes and rods of 
standard sizes, and specify the amount of thermit to use in each 
case. 

In this appHcation of thermit, it should be noted that the 
thermit steel does not come in contact with the pieces to be welded, 
nor does its substance form a part of the weld. Accordingly, 
thermit butt-welding is applicable to pipes and rods of wrought 
iron and mild steel, and not to cast iron and high-carbon steel. 




Fig. 76. — Clamps and 
mold in place for weld- 
ing vertical pipe. 



140 WELDING 

This process can be used for welding gas and water pipes 
while in the ground; steam and ammonia and compressed-air 
pipes; pipe coils, before or after bending; steel rods in reinforced 
concrete. 

The entire cost of making one weld for a pipe of i-inch bore 
is approximately $22. This includes the total cost of the appa- 
ratus necessary, and the time charge of one hour at thirty 
cents for the operator and twenty cents for the helper. This 
prohibitive cost is rapidly reduced for welds in number, just as 
the cost of a printed page rapidly decreases as the number printed 
increases. One hundred welds like the above would cost, ap- 
proximately, one dollar each, supposing that two welds could 
be made per hour. The first cost of tongs and clamps is final, 
while the crucible must be replaced after about ten firings and 
the mold after fifty welds. The cost of the thermit and the 
ignition powder and also the labor is a constant. 

One of the rivals to this welded joint is the plumber's sleeve 
joint. In comparing the two methods of joining, the contractor 
must consider several things; will it be cheaper to cut a thread 
on each pipe end and sleeve the joint? Also, will it be possible 
for the workman to get at his joint to cut the thread ? Is a leak 
at the joint going to be a vital matter? A weld cannot leak, 
while any other joint is apt to under pressure, especially where 
the pipes are cold, as in ammonia plants. Will a sleeve joint 
be strong enough in cases where the pipes are subject to strain ? 
And, finally, how do the total costs compare? This last will 
depend largely on the number of joints to be made. 

Another rival is the oxy-acetylene-blowpipe weld. It is 
probable that with this method one workman can make from 
one to four welds an hour, depending on the amount of labor 
he must put on cutting and fitting the pipe ends preparatory to 
welding. This, together with the cheapness of the gas used, 
makes the operating cost much less than the thermit butt-weld. 
However, the cost of the apparatus, two gas storage tanks, the 
blowpipe, and the checks-valves is much greater. Also, to 
travel from pipe to pipe, often necessary, the operator would need 
an assistant to carry the heavy tanks, etc. 

Butt-welding of pipes can be done by the Thomson electric 



THE THERMIT PROCESS I4I 

process. But this process is at a disadvantage here because the 
welding must be carried on in a heavy machine. Whereas, 
when pipes are to be butt-welded, the chances are that they are 
in some out-of-the-way corner of a room or cellar and cannot be 
taken out. 

Mending Defective Castings. — Besides its use in welding, 
thermit is being exploited for the repair of defective castings, 
which is not strictly a welding operation. Also for raising the 
temperature of the ladle before pouring for castings; for poling 
"burnt iron"; for the introduction of nickel, titanium, etc., into 
molten iron; for the formation of alloys; for the reduction of the 
less common metals from the refractory ores and earths. Though 
these last have nothing in common with welding, they will be 
treated of briefly, so that the treatise on thermit may be 
complete. 

In the foundry, in the casting of large and expensive pieces, 
the loss by defective castings is sometimes equal to the price 
asked for the casting, due to cracks, bad flows, breaks, and inop- 
portune blow holes. If the foundryman can save such pieces 
from the melting pot, he will greatly increase his profits. 

For mending small surface defects, where the idea is to replace 
the surface without regard to the strength of the patch made, 
the following method is advised. First, chip out the defect to 
be sure that it is superficial. Heat the casting around the hole to 
a red heat. Then bank a basin of sand around the hole. Place 
a piece of abestos in the bottom of the basin, large enough to 
cover the hole. Pour thermit powder into the basin, using i8 
ounces of thermit for every cubic inch estimated space of hole 
in the metal. If the casting is a large one, use a greater per- 
centage of thermit, as more heat will be needed. Fire the thermit, 
and it will quickly melt the asbestos bottom, and the molten steel 
will be deposited in the hole in the metal. When cool, the pro- 
truding metal is machined off. 

This reaction is too rapid for the complete separation of the 
slag, some of which may be lodged on the junction of the thermit 
metal and the casting. Also, it is likely that the local heating 
will cause weakening stresses in the patch when it cools; while 
it may also be full of blow holes if it cools rapidly, because of 



142 



WELDING 



conduction. It is claimed^ that the shrinkage is so great that 
such a repair is unsafe and useless. 

Thermit may be used for repairing fractures in castings before 
they leave the foundry. If the casting have a piece broken cleanly 




Fig. 77. — Thermit can plunged into ladle. 

off, this may be joined at a less cost than the cost of recasting. 
Also cracks may be drilled out and thermit used. 

Thermit in Foundry Practice. — Thermit may be intro- 
duced into the ladle before pouring for a casting. If the piece 
to be cast is long and thin, or if it has intricate parts which require 
a very hot metal to produce, the temperature of 
the iron in the ladle can be raised by plunging a 
can of thermit into it and holding it at the bottom 
until both thermit and can have burned up and the 
slag has come to the surface. The excess heat of 
the thermit will raise the temperature of the ladle 

(Fig. 77)- 

^ „ ^ How much thermit to use for a given amount 

Fig. 78. — De- . . ° 

tail of thermit of iron cannot be stated definitely — probably 5 per 
P unger can. cent. It depends on the initial temperature of 
the ladle, the demand of the casting, and the cost. The cost 
prohibits its use except for special work, such as the casting of 
stern-posts for ships, and the production of small castings which 
can be made at any time without the capital investment for a 
special converter plant. 

' "Mending a Casting with Thermit," Pat Redington, Foundry, April, 1905. 




THE THERMIT PROCESS 



143 



The company also recommends placing a can of thermit in 
the riser of such a casting as a ship's stern-post. If the post is to 
be a long one, " the metal cools very rapidly during its passage 
through the mold, and becomes so sluggish that the pressure of 
the runner is not sufficient to force the metal up the rising heads 
more than one-half of their length." The thermit can will 
reinforce the heat of the rising metal. 

To prevent "piping" of steel ingots, a can of thermit may be 
plunged into the ingot. The operator waits until the ingot has 




Fig. 79. 



Fig. 80. 



Fig. 81. 



Fig. 79. — Steel ingot showing defective head piping without anti-piping thermit. 

Fig. 80. — Showing ingot with box of anti-piping thermit in position. 

Fig. 81. — Ten-ton steel ingot having been treated with anti-piping thermit. 



begun to solidify. The " pipe " will then begin to form, due to the 
chilling of the steel on the outside and its contraction. Break 
through the top crust, and thrust the can well down into the ingot. 
It will ignite and raise the temperature of the upper part of the 
ingot to remelting. A solid ingot will result (Figs. 79 to 81). 
This is another use for thermit, questionable, because of its cost. 
Poling. — As has been described, the foundryman often 
freshens his "burnt iron," by stirring the ladle with a green stick 
of wood. "Burnt iron" contains oxygen in the form FCjOg. 
This oxid of iron impairs the strength of the iron very much. 



144 WELDING 

By stirring the molten mass with a green limb, the workman 
has added carbon which reduces the iron oxid, as follows: 

2Fe,03+3C = 4Fe+3CO,. 

The limb being full of water also throws out steam which 
causes the iron to boil. This makes the reaction complete through- 
out the mass. When the oxid is all reduced, the ladle is " fresh." 
But this operation, called "poling," lowers the temperature. 
Now "poling" can be done with a thermit can on the end of a 
rod instead of with a green limb. The composition of the 
thermit must be varied so as to have a positive effect on the oxid 
of iron; that is, there must be a slight excess of aluminum. 
Thermit "poling" has the advantage that it raises the tempera- 
ture of the molten iron. But it should not be used except in la- 
dles of steel, because at the heat of molten steel there is complete 
reaction with the excess aluminum in the thermit. While at the 
lower temperature of molten cast iron, the reaction would be 
confined to the thermit can. The excess of aluminum would 
not react on the iron oxid of the burnt mass, and both would stay 
in solution. In other words, the iron would be poorer than ever. 

A better method recornmended by the company is the use of 
manganese with the thermit, though no doubt the thermit can be 
omitted if we do not wish to raise the temperature. Pure man- 
ganese, made " thermochemically, " can be used. Manganese, in 
the form of ferro-manganese and spiegel, have long been known 
to furnace men as a cure for "burnt iron" and a toughener of 
their product. 

W. M. Carr^ is authority for the statement that a large ladle 
can be used for a small converter if thermit be added to the first 
pour in the ladle immediately preceeding the second pour. The 
ladle held 5 tons, the converter 2 tons, the pours were forty-five 
minutes apart. The thermit was poled into the first pour, as 
usual, in a can on a rod. It freshened the iron and raised its 
temperature to about that of the second pour. 

Adaptability.- — In summing up the thermit process as a whole 
it will appear that it is especially suited for welding and repair- 

'" Development of the Thermit Process in Foundry Practice," Foundry, 
July, 1906. 



THE THERMIT PROCESS 



145 



ing large pieces. In pieces ranging below 4 square inches cross- 
section, it has to meet competition with theoxy-acetylene, oxy-gas, 
oxy-hydrogen, electric, and smithing processes. Its application 
to butt-welding is very often the cheapest, handiest, and most 
workmanlike. 

In rail welding it has to compete with the electric process, 
which was the pioneer in this field. 

In welding motor cases for steel cars it has to compete with 
the oxy-actylene process. 




Fig. 82. — ^Fracture on locomotive frame, opened up by drilling and held in place 
by jacks in preparation for thermit welding. 



In welding fractured locomotive frames it is used with success, 
and is evidently as cheap as can be had — certainly, much cheaper 
than the old blacksmithing, for the weld may be effected often 
without dismantling. It is used in their repair shops by many 
of the railroads in this country and abroad for repairing engine 
frames and also driving rods and spokes, and occasionally the 
repair machinery. The Central Railroad of New Jersey first 
introduced thermit in their shops. 



146 WELDING 

It is used for occasional repairs of fractured gun-carriages and 
parts. 

Also for crank shafts, embossing dies, shears, and anvils, in 
cases where it is cheaper to repair than to replace. 

For broken rudder and propeller shafts, skegs, and stern-posts 
of vessels it is invaluable. This is the most notable feature of 
the process. Before the advent of thermit, a break in one of 
the parts named meant the dry-docking of the vessel for weeks, 
the displacing of the part broken and its repairing at great 
expense and trouble, or sometimes its displacement. Besides 
the actual expense entailed, much was lost by having the boat 
out of commission. 

Since the use of thermit for such repairs, dry-docking is still 
necessary, but the whole operation can be gone through with in 
much less than a week; the vessel is not dismembered and the 
weld may be made the strongest part of the piece. Broken 
anchors can be mended in a few hours. As already described, 
there are many instances of such quick, cheap, and strong welds. 

Thermit is almost a new subject. It has been known to the 
repair men since about 1904. It is already a definite success, and 
under the energetic experimentation of the Goldschmidt Co. it 
is likely to prove useful in ways at present unthought of. It is 
likely that special thermits will soon be invented for welding other 
metals than iron and steel. 

Typical Welds. — In the welding of rail joints in quantity 
there are a number of large contracts that have come to notice. 
Among them the joining of the third rail of the Paris subway; the 
welding of 10,000 joints of the Electric Traction Company of Ade- 
laide, Australia; the welding of the Lexington Avenue line in New 
York City. The latter was especially difficult because of the heavy 
traffic. It was impossible to do the job by daylight without 
tying up the traffic. In the early morning hours, when the cars 
run on a ten-minute schedule, the company succeeded in carrying 
on their welding with only the occasional holding up of a car. 

The cost of thermit rail welding has been variously estimated. 
Track at Holyoke,^ Mass., welded in 1904, cost $6.23 per joint. 
The longest unit rail made was 2300 feet. In the same year rail 

^Street Railway Journal, Feb. i8, 1905. 



THE THERMIT PROCESS I47 

welding at Hartford/ Conn., cost $5.00 per joint, which figure 
includes repaying. 

Among pipe-welding contracts, that carried out for the Man- 
hattan Refrigerating Co.," of New York City, is noteworthy. 
Their entire system of piping was welded by the thermit process. 
There were twenty-nine i 1/4-inch joints, and twenty-seven 
2-inch joints, both under a cold pressure of 180 pounds. The 
result is reported as successful. This is a decided improvement 
on the sleeve joint for ammonia systems, because the contraction 
of the pipes due to the extreme cold is certain to allow leakage in 
the sleeve joint. 

Repair of the ''Betsy Ann''^ 

" One of the quickest repairs on record was accomplished on 
the Mississippi River Steamship 'Betsy Ann,' belonging to 
Learned & Son, Natchez, Miss. This is a stern wheel boat, the 
shaft being a hexagonal one, 83/5 inches on the inscribed circle 
and over 23 feet long. A crack developed on one of the faces 
and ran down a short way on the second face, the total length 
visible being about 4 inches. Attention was first called to this 
by rust showing through the paint and after examining the shaft 
carefully it was decided to run the steamer to see if the crack 
extended. Within a short time it was noticed that the crack 
had extended 3/4 inch since the first observation, and it was 
therefore decided that a repair of some sort should be made on 
it at once. Preparations were made to weld a collar of Thermit 
steel around the shaft at the fracture and thus to restore it to its 
original state of usefulness. A pneumatic chipping hammer was 
used for cutting away the metal to the bottom of the flaw, so 
that the superheated Thermit steel could be led to the deepest 
part. After this had been accomplished, the paint was cleaned 
off a distance of 5 inches on either side of the fracture and the 
weld effected by the wax pattern method, as previously de- 
scribed; 416 pounds of Thermit, 35 pounds of mild steel punch- 
ings, and 8 pounds of metallic manganese being required. After 

' Ibid., Jan. 28, 1905. 

- Iron Age, Nov. 16, 1905. 

^Reactions, published by Goldschmidt Thermit Co. 



148 



WELDING 



allowing five hours for the metal to set, the mold box was re- 
moved and the weld found to be so satisfactory that the steamer 
immediately proceeded on her trip without waiting for the gate 
and riser to be cut off; in fact, the repair was accomplished 
without causing the steamer to miss a single trip." 




Fig. 83. — Finished weld of S. S. "Betsy Anne" before removing metal left in gate 

and riser. 



Repair mi Steamship ''Corunna'' 

"This was a vessel of 1296 tons register, 240 feet long, 35 
feet beam and 21 feet depth. In getting away from her pier in 
the Lachine Canal, Montreal, the stern of the vessel was caught 
by the current and swung against the stone walls of the canal, 
the shoe or skeg being broken off close to the keel, while the 
rudder-post was broken at a point about 10 inches from the top 
of the rudder. Owing to the serious nature of the injuries it 
ordinarily would have been necessary to tow the vessel to Cleve- 
land (there being no adequate dry-dock in Montreal to make 
these repairs in the usual way). 



THE THERMIT PROCESS 



149 



"It was soon decided that, without doubt, several thousand 
dollars could be saved by repairing the frame and rudder-post 
with Thermit, 

" On inspection it was found that the rudder-post was broken 
off inside of the tube, while the stern frame had been bent 12 
inches out of line, the shoe being completely broken about 13 
inches from the central line of the post. On account of the 
break in the rudder-post being by an old scarf weld, fully 11 




Fig. 84. — Finished weld on rudder post of steamship "Corunna." 

inches in length, it was not deemed advisable to attempt to weld 
this again, so about 14 inches of the rudder-post adhering to the 
rudder was cut ofif and a new piece of shafting, 8 feet long, 
welded on in place of the old post, as shown in the illustration. 
In order to facilitate the operation, the rudder was removed 
from the ship and the post welded on shore, this being done to 
prevent interference with the operation of welding the stern frame, 
" It being necessary to have a supply of compressed air in 
order to operate the gasolene torch and pneumatic tools, an old 
Westinghouse steam-driven air-brake compressor was obtained 



ISO 



WELDING 



and mounted on board ship, the steam being piped from a 
donkey boiler. A receiving tank was placed on the edge of the 
boiler and piped to the compressor. With the apparatus in 
place, preparations were made to effect the welds in the usual 
way, the rudder-post weld being reinforced by a collar 3 inches 
long and i inch thick, while the stern-post was reinforced with a 
collar 8 inches long, i inch thick at the top and sides, and 3/4 



^iMmMMBm^I^^B 


V 


Ij 




'' Wi! ! 1 






d 



Fig. 85. — Thermit weld on stem post of steamship "Sochem." 



inch thick at the bottom; the latter being done in order that the 
draught of the vessel might not be made any greater than could be 
helped. One hundred and fifty pounds of thermit, 25 pounds of 
steel punchings, and 3 pounds of metallic manganese were used 
in welding the rudder-post, while 350 pounds of thermit, 70 
pounds of steel rivets (i by 3/8 inch in size) and 7 pounds of 
metallic manganese were required for welding the stern frame. 
"While the total time required for the operation amounted to 



THE THERMIT PROCESS I5I 

five working days, there is little doubt that had the work been 
done in a properly equipped dry-dock, it could have been ac- 
complished in three days or less." 




Pig 86.— Weld made at shops of the central railroad of New Jersey on a motor 

armature shaft. 

Weld of Electric Motor Shaft 
" It has usually been deemed necessary to leave a reinforce- 
ment or collar of thermit steel around the various welds made 
by the thermit process. An instance has occurred recently, 



152 WELDING 

however, where this reinforcement was machined off and the 
weld subjected to ^"ery severe strains, but without causing any 
weakness to show up. 

" The case in question is that of an armature shaft 3 inches in 
diameter, 14 1/2 inches long, and required to transmit 50 h.p. 
to the main hoist of a 50-ton Shaw electric crane. 

"The weld was made in the shops of the Central Railroad of 
New Jersey, Elizabethport, N. J., and the armature has now been 
in service since October 8 and is giving perfect satisfaction in spite 
of the fact that all the surplus metal about the weld was machined 
off and the shaft turned down to its original diameter. 

"The weld was made 9 inches from the hub, and is shown in 
the accompanying illustrations" (Fig. 86). 

Chemistry and Thermics. — The chemical formula for the 
present thermit reaction is 

8A1 +3Fe30, = 9Fe +4AI2O3. 

Expressed in weights, it is 
217 parts aluminum +732 parts magnetite = 540 parts metallic 
iron +409 parts slag, 

or, approximately, 3 parts of aluminum and 10 parts magnetite 
will produce, on combustion, 7 parts metallic iron. 

Commerical thermit is a mixture of finely granular aluminum 
with less finely granular magnetic iron scale. The aluminum 
is about the fineness of granulated sugar; the scale is like coarse 
sand. The ratio by weights is three of iron scale to one of alum- 
inum. Dr. Goldschmidt began his experiments with similar 
mixtures about 1895. Thermit was not heard of before 1902. 
He speaks with feeling of the mechanical and chemical diffi- 
culties that hindered the perfection of his ideas. So there is 
good reason to suppose that the thermit mixture is about the 
best that can be made, both in its physical form and in its reac- 
tion. The difficulties that confronted Dr. Goldschmidt were: 

1. The violence of the reaction. 

2. How to get a good homogeneous steel out of the reaction. 
One of the troubles with thermit reactions is their violence. 

The burning of several metals, as calcium, is so brisk that the 
contents of the crucible boil over and metal and slag alike are 



THE THERMIT PROCESS 1 53 

lost. Probably for this reason the magnetic oxid was substituted 
for the hematite oxid. Early literature gave the reaction as 

2Al+Fe203 = Al203+2Fe, 

but Dr. Goldschmidt^ gives the present reaction as between 
aluminum and magnetite, and a casual examination of thermit 
by means of a magnet shows that magnetite is now used. It is 
likely that the magnetic oxid gives a slower burning than does 
the sesquioxid. The magnetic oxid is made of granulated roll- 
ing-mill scale. 

The aluminum is powdered by a secret process. At present 
there are two known ways of pulverizing metallic aluminum. 
The first is to raise the metal to an approximate 600 deg. Cent., 
at which heat the metal becomes brittle and granular, and can 
be ground between rolls. The second way is to blow air through 
red-hot aluminum so as to partly oxidize the metal. It is then 
cooled to about 600 deg. Cent, and ground, the oxid of aluminum 
helping to separate the metal into fine granules. 

As will be guessed, a small amount of thermit will burn more 
slowly than a large amount. The heat of a large burning, such 
as for repairing a propeller shaft or large engine fly-wheel, will 
be so intense that the crucible will boil and throw out part of 
its contents. To prevent this, from 5 to 15 per cent., by weight 
of thermit, of cold steel billets and turnings are added to the 
thermit before burning. This iron takes up the excess heat. 
Of course this added steel must be of correct chemical composition. 

While it is important to keep down the boiling reaction, it is 
even more necessary to get a resultant steel that will be strong, 
elastic, and dense. The quality of the thermit steel will depend 
on its chemical composition. Good steel is low in sulphur, 
phosphorus, and silicon, and not too high in carbon. The follow- 
ing "Average Composition of Thermit Steel" is given by the 
Company : 

Carbon 0.05 to o.io 

Manganese 08 to .10 

Silicon 09 to .20 

Sulphur 03 to .04 

Phosphorus 04 to .05 

Aluminum 07 to .18 

' Electrochemical and Metallurgical Industry, Sept., 1908. 



154 WELDING 

Of course, to produce a steel of the above composition, the 
aluminum and iron scale that make up the thermit must be very- 
pure. It would be a problem to obtain sesquioxid of iron of 
sufficient purity and at the same time as cheap as rolling-mill 
scale. Sesquioxid or hematite ore always contains one or the 
other of the impurities in considerable extent and is of variable 
composition; while, in using scale from Bessemer or open-hearth 
steel the impurities would be already known and would be much 
lower. 

In regard to the proportioning of the mixture, the formula 
calls for 3 parts of aluminum to lo of iron oxid; the thermit 
mixture is i of aluminum to 3 of the oxid. 

In nickel thermit the reaction is 2AI -(-3NiO = AI2O3 -f 3Ni. 
By weight, it is 54 parts aluminum and 224 parts nickel 
oxid give 176 parts metallic nickel. Or, approximately, i part 
aluminum and 4 parts nickel oxid give 3 parts metallic nickel. 
Nickel thermit, however, contains 5 parts of nickel oxid by 
weight to 5 of aluminum. 

Besides the aluminum-iron oxid reaction, a number of others 
have been and are being tried. It is possible that the future 
thermit may dispense with aluminum and substitute another 
metal for reducer. " Weldite," an English product, uses silicon 
and aluminum with FCjOg. Dr. Goldschmidt himself has tried 
other combinations: for instance, aluminum and calcium, which, 
according to Dr. Richards,^ give a greater heat due to the forma- 
tion of calcium-aluminum slag. He gives the probable formula 

5Fe203+3CaAl2 = 3(FeO.CaO.Al,03)+7Fe; 

and claims that 70 per cent, of the iron would be reduced from 
its oxide; and that one part calcium-aluminum alloy will produce 
one and four-tenths of liquid iron (metallic). 

Calcium^ alone can be used to replace aluminum, but the 
reaction is so violent that sometimes the contents fly out of the 
crucible. The addition of 30 to 40 per cent, fluor-spar (CaF) or 
10 to 20 per cent, quicklime (CaO) gives a saner reaction. 

Heat of Reaction. — Richards" has calculated the heat of the 
thermit reaction as 2694 deg. Cent. The temperature commonly 

' Engineering and Mining Journal, June 15, 1907. 

^ Electrochemical and Metallurgical Industry, J. W. Richards, June, 1905. 



THE THERMIT PROCESS 155 

given by the manufacturers is 3000 deg. Cent. M. Fery, using his 
new radiation pyrometer, found the temperature of the stream 
of steel as it flowed from the crucible to be 2300 deg. Cent — 
probably about right when one makes allowance for the chilling 
effect of the crucible. Taking the melting point of steel as 
roughly 1350 deg. Cent., the thermit steel is nearly twice as hot. 

Testing. — The strength of an ordinary weld in wrought iron 
varies from 10 to almost 100 per cent, of the strength of an equiv- 
alent cross-section of the metal. In general, however, a weld 
made under proper conditions runs between 50 and 70 per cent, 
for high-carbon iron and between 60 and 80 per cent, for low- 
carbon iron. The strength of a thermit-weld is subject to quite 
as great variance, for the reason that thermit steel is a definite 
compound and may be -of quite different composition from the 
parts welded by it. Also it is well to bear in mind that the initial 
strength of thermit steel itself is subject to variations due to the 
amount of included slag, air holes, and to the rapidity of cooling; 
also, the chemical composition can be varied by the addition of 
alloy formers, such as nickel, chromium, and manganese; and 
the addition of titanium and manganese in small quantities, which 
are purifiers. 

A number of tests of different character have been made by 
the company and by railroad and repair shops, some of the results 
of which are given as follows: 

Test No. i} 

"At the St. Louis and San Francisco Railroad shops, Spring- 
field, Mo., recently the following test of a thermit- weld was made: 

"A section of a cast-steel frame, 4 by 5 1/2 inches, was welded 
by the thermit process. In making the weld 75 pounds of ther- 
mit, 12 pounds of punchings, and i 1/2 pounds of manganese were 
used. For molds, fire-brick was used, cut to shape. 

"After the weld was cold, the collar on the bottom and one 
side was planed off 1/4 of an inch below the original surface of 
the casting, in order to show the place where the two metals had 
joined. The riser also was cut off, leaving the collar, however. 
The weld was absolutely solid, not a single blow hole appearing 
anywhere — not even the riser. 

' Reactions, Vol. I, 1908, published by Goldschmidt Thermit Co. 



156 



WELDING 



"The welded section (now 3 3/4 x 5 1/4 inches), with collar 
I inch thick on top and on one side, was then placed in wheel 
press on supports 14 3/4 inches apart and a piece of hardened 
steel, I inch square, placed as shown in figure 87. 

"A pressure of 170 tons was applied before breaking. The 
fracture started at the bottom outside welded section, extending 
into the center of the weld at the top. The fracture showed that 
perfect amalgamation of the metals had taken place. 

"In comparing the strength of this weld with original stock, 
assuming a maximum stress in the outer fiber for cast steel of 




r— 64— ^ 



Fig. 87. — Arrangement of test piece for test No. i. 



60,000 pounds to the square inch, a section 3 3/4 x 5 1/4 inches 
tested in the same way would break at 100 tons." 

In this test No. i it is presumed that the 12 pounds of 
punchings were mild steel. The manganese was used to freshen 
the iron, and most of it probably slagged as manganese oxid and 
came to the surface. 

Test No. 2. ' 

"Two test bars taken from the upper part of a previously, 
but unsuccessfully, poured casting gave, on an average, 66,000 
pounds per square inch tensile strength and 9. 5 per cent, elonga- 
tion on a measured length of 2 inches. This casting showed in 
all the sections a clean, non-porous, dense grain. It appears 
possible, therefore, to produce steel castings of thermit and, in a 

' Iron Age, April 26, 1906. 



THE THERMIT PROCESS 



157 



case of necessity, the higher price would not be of importance." 

H: 4: >{: "L 

Test No. 3. 

The thermit process has been used by the Fore Shipbuilding 
Co./ of Quincy, Mass., who have made a number of tests of the 
physical properties of thermit metal. Bars of rolled steel, of 
section 2x4 1/2 inches were drilled, broken, and welded with 
thermit. Standard test bar were cut from the centre of the 
welded bar, and were submitted to the ordinary tests. As the 
test pieces were of uniform size, both in the stock and the welded 
section, the result is worth recording: 





Elastic limit 


Tensile strength 


Weld 

Stock 

Weld 

Stock 


32,000 
38,000 

33>7oo 
36,850 


59,000 
60,500 
61,800 
63,400 





It is to be noticed that the tensile strength is 12.7 per cent, 
less in the weld than in the stock, and the tensile strength 2 . 5 
per cent, less — a fair showing. 

Test No. 4.— By the Illinois Steel Co., Chicago.'' 

C 0.05 

Mn 10 

Si 204 

S 04 

P 05 

Al 18 



Tensile strength 59,32° lbs. 

Elongation 25 . 33 per cent. 

Contraction of area ... 59.9 per cent. 



Test No. 5.— By the Pennsylvania Railroad, Altoona, Pa.= 



C o. 102 

Mn 2.330 

Si 1.227 

S 034 

P 07 



Tensile strength 91,600 lbs. 

Elongation in 8" 21.5 per cent. 

Silky fracture. 



^Journal United States Artillery, Gustav Reiniger, July-August, 1907. 
^ Transactions of the Society for Testing Materials, E. Stutz, IQ05. 
^Transactions of the Society for Testing Materials, E. Stutz, 1905. 



1 58 WELDING 

Test No. 6. — It has been suggested that the thermit-weld 
may be strong in itself, but that it weakens the adjacent iron. To 
find if this is so, a section of welded rail was subjected to equal 
blows by a steam hammer, both on the unaffected rail and on 
the metal nearest the weld. The die used was a blunt tool, 1/4 
inch in diameter. Measurement with a micrometer showed a 
depression of o. 1432 inch in the rail nearest the weld and o. 1596 
inch 3 feet from the weld. 

Tests, under varying conditions without number, might be 
multiplied. But for the practical man, those already given show 
that the ultimate strength of the thermit steel in practice can be 
estimated as over 30 tons to the inch section. By practice, I 
mean the thermit steel produced for repair work, according to 
directions: thermit, about 5^ per cent, mild steel punching, and 
about 2^ per cent, manganese for purifier. 

Annealing for 3 hours brings the elongation well over 10 per 
cent. 

Addition of about 3^ percent, nickel raises the ultimate strength 
about 5 tons without decreasing the elastic limit. Further addi- 
tion of about 2^ per cent, of chromium with the nickel brought the 
elastic limit to about 47 tons — as high as can be wished. Addi- 
tion of I per cent, titanium raises the tensile strength. Tests have 
also been made of thermit steel that has been toned up with 
molybdenum, ferro-silicon, etc. 



THE LAFITTE WELDING PLATE. 

The Lafitte process was first heard of in 1905.^ It may be 
described as the handy application of a patent fluxing sheet be- 
tween parts to be welded, and can only be used for joining iron 
and steel. The flux is sold as a plate, size 4 by 8 inches and 
about 1/16 inch thick. This plate is composed of a preparation 
of calcined borax and iron filings, molded over a sheet of wire 
gauze. The gauze is about 15 meshes to the inch length. 

' Calculated from weight of thermit powder. 
^ Calculated from weight of test bar. 
^ Iron Age, May ii, 1905. 



THE LAFITTE WELDING PLATE 



59 



The iron of the wire is low-carbon (0.08 per cent, by color 
determination^). 

The pieces to be welded are brought to the welding heat and 
forced together with a Lafitte plate between the contacts. As 
with all smith-welding, one of the contact surfaces should be 
decidedly convex, so that the point of it is first brought to bear 
on about the middle of the other contact surface. As the two sur- 
faces are forced together, with the plate between, the borax melts 
and flows out, fluxing both surfaces as it flows. The iron gauze, 
which is inside the plate, is also partly melted and welds itself in 
place on both surfaces. It is likely that the strength of the Lafitte 
weld is as much due to the binding action of this low-carbon iron 
wire as it is to the complete fluxing of the borax. If properly 
done, the weld should be flawless. It is not necessary to use more 
of the plate than will cover both surfaces. The plate can be cut 
with ordinary shears. 

From tests made it is claimed that the Lafitte weld is as strong 
as the metal, in case soft steel is welded; but that in high-car- 
bon steel there is a slight lowering of the elongation and tensile 
strength (due no doubt to the reheating of a specially treated 
product). 

In all but one of these tests the tensile strength is greater for 
the Lafitte weld than for the body of the stock, which may indicate 
that an upset of metal was crowded into the weld by the pressure 
of welding; while with cast steel the quality of the metal might 
be improved by the pressure. 



Hard Steel Test 
Mn, 1.35; C, 0.45; S, 0.045; P, 0.083; Si, 0.08 



Tensile strength, kg. . 


Before welding 


Lafitte weld 


Common weld 


70 


63.6 
68. 


55-9 


Elongation, per cent. . 


15.2 


lO.O 

11.6 


2-5 



' Specially analyzed. 



l6o WELDING 

Test by the French Government' — (Toulon Arsenal) 





Tensile strength, lbs. 


Elongation, per cent. 


Before 


Special 
compound 


Lafitte 


Before 


Special 
compound 


Lafitte 


Iron on iron 

Iron on soft steel 

Stsel on soft steel .... 
Iron on cast steel .... 
Cast steel on cast steel. 


48,700 
48,700 
75.935 
75,935 
95.030 


44,729 
43,964 
72,197 
43.719 
92,712 


48,938 

45,631 

80,500 

78,692 

102,711 


16.33 

16.33 

2. — 

2. — 

S.62 


9.66 
4. — 

3-25 
3- — 


14.33 
4. — 
2. — 

9-05 

5-— 



The Lafitte method may suggest itself for stock welds, such 
as the joining of axle parts and in chain making; in other words, 
in instances of multiple welding, where the pressure machinery 
is handy. It is most used in France and Germany. 

FERROFIX BRAZING PROCESS 

An ingenious and very good modern method of brazing 
broken iron parts (especially cast iron) goes by the name of the 
Ferrofix Brazing Process. It was devised by Frederick Pich, a 
German, By this process two fractured pieces of iron are ce- 
mented together with a thin film of brass which is so applied that 
it alloys with the iron surfaces, as deep as 1/16 inch. This 
was proven by cutting open a brazed joint and planing it 
down to ascertain its structure. To get this alloy in the joint, 
which is the secret of its strength, the solder must not melt below 
650 deg. Cent.; hence hard brass is used. 

Apparatus for Ferrofix repairing consists of: 

1. A kerosene pressure tank and two or more Donnelly torches, 
which is an improved non-carburizing kerosene burner. 

2. Fire-bricks and asbestos paper for a small furnace, 

3. Ferrofix fluxing powder. 

4. Patent brazing liquid. 

The torch for heating may be air-coal gas, air-oil, oxy-acety- 
lene, etc. 

The flux is a mixture of equal parts of sodium carbonate and 
boric acid, with a little common salt to increase fluidity. 

^Iron Age, August 24, 1905. 



■ FERROFIX BRAZING PROCESS l6l 

United States patent paper, No. 688030, states that borax, 
the chief flux for all soldering and brazing, is troublesome be- 
cause it swells up and falls off of the piece as soon as heat is 
applied. This, because it is then parting with water of crystal- 
lization. The patent flux, on the other hand, acts as follows: the 
carbonate is a ready absorbent of grease, of which it frees the 
the iron surface. With the application of heat, the, carbonate also 
reacts on the boric acid, forming anhydrous borax and carbon 
dioxid. The borax is thus in close contact with the fresh metal 
surface, which it frees of rust and protects from the air. 

The soldering compound is described in patent No. 647632 as 
follows : 

*'To form my improved soldering compound, I boil together 
finely pulverized borax and finely pulverized suboxid of copper, 
so that the same are intimately mixed and so that each particle 
of the suboxid of copper is surrounded, covered, and protected 
from the atmosphere by a thin film of the borax. Any desired 
proportions of the two may be used; but usually I take one-half 
of each, mixed with sufficient water to dissolve the same thoroughly 
by the boiling, and to cool down into a sort of paste. 

"To use this soldering compound, the cast-iron surfaces to be 
soldered are cleaned by means of an acid in the usual way, fixed 
together, and the joints covered or surrounded with the compound. 
The joint is then heated, and therefore the borax melts and pro- 
tects the cleaned surface of the iron against oxidization, removes 
any oxid thereon, and also protects the suboxid of copper against 
the action of the oxygen of the atmosphere. Consequently 
the suboxid of copper, likewise heated to a red heat, transfers 
its oxygen to the red-hot cast-iron surface, which oxygen com- 
bines with the graphite contained in the cast-iron surfaces to 
form carbon monoxid or dioxid, thus decarbonizing said surfaces, 
while the metallic copper becomes dissociated in a very finely 
divided condition. At the same time the hard solder is added, 
and as this solder, which is brought upon the surfaces to be sol- 
dered in the well-known manner, is likewise melted by the heat, 
it alloys itself with the incandescent particles of copper, and this 
new alloy immediately combines with the red-hot decarbonized 
soldering surfaces of the cast iron." 



l62 WELDING 

The company also issue instructions, which are in brief: 

I. " Clean fractured surfaces thoroughly with wire brush. If 
rusty or oily, burn off with torch. 

" 2. Mix Ferrofix powder with the brazing liquid to the con- 
sistency of paint and apply on the fractured surfaces with brush. 

" 3. Set casting to be brazed on fire-brick, in perfect alignment, 
using fire-clay to hold it in place (if it will not stay of its own weight) . 
Be sure that the broken parts fit close. Build a furnace of fire- 
brick around the fractured part, allowing sufficient metal to be 
exposed, however, to absorb the heat. Leave top of furnace 
open, covering only with a sheet of asbestos — 3/16 inch thick is 
sufficient ordinarily. The front of furnace should be left open to 
admit the torch blast. 

"4. Place the torches so that the flame will come directly on 
fracture; bring casting up to a light cherry-red, almost straw. 
See that both sides of the fracture keep at the same color. 

" 5. Apply flux with a steel spoon (made from 3/8-inch Besse- 
mer steel rod flattened out at one end) holding it at the fracture 
with the spoon, so that from the heat of the casting (not the 
torch alone) it will melt and disappear through the crack. As 
soon as it comes through freely and you can see the liquid flux 
underneath, apply spelter with a very little flux; feed this until 
it flows through thoroughly. With the spoon the melted brass 
can be taken from underneath and fed over until the crack com- 
mences to fill, then cut off immediately your air and gas, and keep 
feeding a little more new brass until it will not melt further by 
heat of casting. Allow to cool down by its own cooling. 

"6. Clean casting with file, chisel, or emery wheel. 

"The question of expansion and contraction is governed by 
the construction of the casting and the character of the metal. 
Care should be taken to see that heat is properly applied and 
distributed to overcome this feature. Experience on intricate 
castings is the best teacher." 

This is another comparatively new process that is beginning 
to be known by the foundries, car shops, blast furnaces, and 
machine shops. The first patent dates 1900. Its success is 
based on its cheapness, handiness, and strength. The initial 
expenditure is very low, the burner costing most. The outfit 



FERROFIX BRAZING PROCESS 



163 



would prove a great saving to any plant which has breaks in its 
iron machine parts. For a fractured piece could be mended in 
an hour, whereas it is ordinarily necessary to rivet the old piece 
together with side braces or to order a new piece under danger of 
delay and hold up. 

As for strength, the company guarantees that the joint is 
stronger than cast iron; brazed pieces never break in the joint. 
Moreover, the pieces to be mended are set as closely as possible, 
as the spelter will penetrate the tightest fracture. 

There are "several tests covering the penetration of brass on 
cast iron treated with Ferrofix and also untreated. This was 
done by the taking three test bars which had the upper surface 
smooth, one was left uncoated, one had one coat of Ferrofix 
applied, and the third had two coats of Ferrofix, They were 
then placed in the furnace and heated to the same temperature, 
and the surface coated with brass as in brazing. When cold 
the coated surface was planed 1/32 inch below the original surface. 
We found on the untreated piece no evidence of brass, while 
on the treated pieces brass was distinctly discernible in the pores 
of the iron. Another 1/32 inch was then taken from the two 
treated pieces, and we found on the bar that had a single coating 
of Ferrofix minute traces of brass, while on the double-coated 
piece the brass was very distinct. It must, therefore, be apparent 
that the joint we obtain is not simply a surface adhesion, but an 
actual anchoring of the filling material to the adjacent faces of 
the fracture."^ 

Tests Made by Riehle Bros. 

Specimens 6" x 6" x 24" long. Cast iron. Supports 20" apart. Load applied 
at center of specimen. 



Marked 


Breaking strength in lbs. 


After brazed 


I 
2 
3 
4 

5 


155,280 
178,700 
194,440 
168,700 
163,220 


131,000 
180,860 
187,750 
178,310 
162,450 



' Special information. 



164 



WELDING 
Tests Made by Riehle Bros. 



Marked 


Area in sq. 
inches 


Ultimate strain 
persq.in. inlbs. 


Remarks 


No. I. Brazed 

No. 2. 

No. 3. Solid 


.450 
•439 
•439 


19,220 

20,570 
22,730 


Broke outside weld 
Broke outside weld 
Broke 



Two other tests by the same company showed increases of 
I and 6 per cent, for mended bars. 

Of three tests by Lewis Foundry and Machine Co., the j&rst 
showed an increase in strength of i, and the other two a decrease 
of 14 and 29 per cent. 

Two bars tests by Cramp's broke outside the joint. 




Fig. 



88. — Broken arm that was made stronger than originally by the ferrofix 
brazing process. 



The process is now used for all-sized repairs, small or very 
large. 

"By accident a spoke was broken from a fly-wheel, 19 feet in 
diameter, 48 inches width of rim, weighing 21 tons. A new 
wheel would have cost $2700 and would have involved two or 
three months' delay. The Pich process was applied; the broken 



BRAZING AND SOLDERING 165 

spoke was brazed into place, and $250 charged and paid for the 
job. The actual cost of doing this work was less than $50/ 

Figure 88 shows a break of an important appliance that can 
be mended by this process. 

BRAZING AND SOLDERING 

Brazing and soldering are processes which are much like 
welding and which often shade over into welding. The brazing 
of brass is welding, except that the metal is not pounded together, 
but melted. The definitions for soldering and welding are given 
in the first chapter. Brazed and soldered joints resemble welded 
joints in as far as the solder and the metal of the piece or utensil 
amalgamate at the joint. But such joints are different from 
welded joints because the solder or spelter is of different com- 
position from the metals it joins and serves the purpose of a 
go-between. 

Brazing. — Iron, brass, copper, gold, and silver are the metals 
joined by brazing. The process is briefly: fluxing the metals 
at the joint, adding the brazing mixture called "spelter," heating 
until the spelter melts and works into the joint, finishing the 
brazed joint with the proper tools. 

The flux used is either borax or boracic acid. The latter 
is used because it is cheaper; but for other than rough, commercial 
work borax is the btter. Borax should be burnt or calcined 
before using to drive off the water of crystallization. If this is not 
done, the borax will swell up under the flame, will blister, jump, 
and much of it be lost. Whereas calcined borax simply melts on 
the metal, runs over the surface in a thin glass, and cleans the 
surface of oxid and grease. 

Before applying the flux, it is well to clean the metal with a 
file and remove all grease with a rag or alkali water. 

Besides borax there are a number of other chemicals which 
can be used, such as zinc chlorid, sal ammoniac, common salt, 
and the corrosive acids. None of these are as good as borax. 
The first two are properly soldering fluxes, the third melts too 
readily, and the acids are liable to remain in the brazed joint 
and to decompose it slowly. 

^Proclamation of the Boston Society of Civil Engineers, May 20, 1903. 



166 



WELDING 



A number of patent powders and liquid fluxes are now on the 
market. They are mixtures of the common fluxes in such form 
that they can be easily applied to the work. 

Spelter for brazing is used to cover a range of hard and soft 
alloys, though spelter is supposed to be a half-and-half alloy of 
copper and zinc. Hobart^ gives the following table of brazing 
alloys: 



Brazing alloys 


Tin 


Copper 


Zinc 


Antimony 


Hardest 

Hard (spelter) 

Soft 

Softest 


o 
o 

I 

2 


3 

I 

4 
o 


I 
I 

3 
o 


o 
o 
c 

I 



English books mention spelter as composed of i part of 
fine brass, i part zinc — in other words, 2 parts zinc, i part cop- 
per. The hardest spelter will give the strongest joint, provided 
the spelter amalgamates perfectly at the joint. It will also 
require the hottest flame to melt and will be more difficult to 
handle. Softer spelters give softer joints, work in easier, and are 
cheaper to handle. Brass and iron joints that do not have to 
stand strain nor long time test are brazed with softer spelters. 
Spelter is powdered or filed into shavings, and mixed with the 
flux; or it is cut into thin strips or small chunks. 

The torch, for brazing or soldering, is used when the work is 
not on a large piece or when a forge is not handy. A gasoline 
or kerosene torch can be used for small work. A blacksmith's 
forge is better, because the piece can be heated slowly and evenly, 
and cooled the same way. The same restrictions apply for all 
fuel used as apply for welding (see page 4). The fuel should 
be free from sulphur and soot and the flame should be non- 
oxidizing. In the case of coal and coke, do not let the fuel touch 
the parts to be brazed. 

As in welding, a gas flame is the best. The operator can build 
up a furnace of fire-brick, with one or more nozzles of gas pipe 

' "Brazing and Soldering," James F. Hobart, 1908. 



BRAZING AND SOLDERING 



167 



intruding. He can then regulate the size and direction of the 
flame, and heat and cool the work slowly and evenly. 

Brazing work requires high temperatures: for iron it is done 
at a bright red, almost white, heat. This explains why the flame 
should be reducing and free from sulphur. 

The gas flame varies from a blowpipe flame to that given by 
a two-way injector tube made of gas piping (see Fig. 89). The 
flame is a bunsen flame, with a blue cone. 

To braze requires considerable variation in practice, accord- 
ing to the work at hand. Suppose the worker is about to braze 




Fig. 89.— Air-gas torch for brazing. 



together two cast-iron pieces of a fractured bar. He first cleans 
the ends of the bar at the fracture by filing and scraping away 
all grease and paint and then cleans the fracture with a wire 
brush. He then brushes the borax on the fresh surfaces or, in 
case a liquid preparation is used, he applies it with a brush. 
He then places the pieces together as he intends to braze them, 
resting them on fire-brick, and bmlds up a little oven of brick 
around and over the pieces, leaving one wafl of the oven open 
for the flame (see Fig. 90). When brazing pieces or mending 



i68 



WELDING 



fractures, always press the surfaces as closely together as possible. 
No joint is too tight for the spelter to enter, while the tightest 
joint will be the strongest. 

The burners are then brought up in front of the open oven 
and pointed at the work. These burners, for job work, are com- 
monly made of two-way gas pipe with rubber hose for leading 
tubes. One tube carries the gas, the other the air blast. The 
air-blast tube is straight and draws in the gas by injection. The 
air blast is made by a motor-driven fan. For convenience these 
gas-pipe torches are swiveled on tripods. The air blast is 
started, the gas turned on, and the operator regulates the flame 




Fig. 90. — Makeshift brick furnace for brazing; showing broken casting in position. 



to an even blue cone by turning the cocks. The flame is di- 
rected at the work and kept there until the brazing is done. At a 
bright red heat, the operator sprinkles more brazing powder or 
borax on the edges of the fracture, and works it back and forth 
with an iron spatula. This cleans the iron surfaces at the 
fracture, so that the spelter will wet the iron and run down into 
the fracture; next he shovels some spelter over the fracture and 
works it back and forth as it melts down. If the fluxing has been 
right, the spelter will slip down into the crack and fill up the entire 
fissure, wetting the iron surfaces, and the excess will run out of 
the lower crack of the fracture. 

The operator now turns off the flame and allows the work to 
cool. Cast iron will cool quickly; but if the piece to be mended 



BRAZING AND SOLDERING 169 

is at all intricate or has long arms, care must be taken to allow 
for equal cooling and shrinkage. 

Care must be taken in heating the work to be brazed that the 
heating is done evenly and that no part is overheated. In the 
case of brass, overheating spoils the metal as it burns out the 
zinc to some extent. A safe method in brazing brass is to paint 
the piece over with a graphite preparation, except where the 
brazing is to be done. The graphite is indifferent to flame and 
flux and will prevent the zinc from volatiHzing. One of the 
objections to soft spelter is the amount of zinc it contains. 

In the making of a number of utensils brazing plays an impor- 
tant part. For this reason it is important to do the work quickly. 
Much repeat or stock brazing is now done by immersion, the same 
as iron is tinned. The pieces to be brazed are painted with 
graphite wherever necessary, are heated, and then plunged into a 
bath of melted spelter, on the top of which floats the melted flux. 
The flux cleans all of the metal unprotected by the paint, and 
then as the pieces are lowered further into the bath, the melted 
spelter readily wets the fluxed surfaces and brazes the pieces. 

In brazing gold and silver, the alloy used is commonly a 
mixture of spelter with gold and silver; sometimes antimony, 
arsenic, etc., being added to reduce the melting point and to make 
the alloy fluid. This means that the process is really a soldering 
one. Brazing of gold and silver is a jeweler's art. It is done with 
small pieces and needs only a foot blast or a mouth blowpipe for 
the flame. 

A brazed joint is commonly considered to be stronger than 
the adjacent metal. A brazed cast-iron piece wfll never frac- 
ture at the braze. Tests of well-brazed joints show them to 
to be from lo to 25 per cent, stronger than the iron. A brazed 
joint is inferior in a number of ways to a welded joint. In the 
first place, the electrical conductivity is not equal to the piece, 
brazed. Then there is the danger that free acid, pieces of flux 
or rust have been left in the joint and will lessen the strength at 
once or by slow action. Then, under water, a brazed joint may 
become an electric couple, and the metal may slowly disinte- 
grate. Lastly, it is found that brazed joints will not stand concus- 
sion tests as well as welded joints. This is attributed to the 



1 70 WELDING 

presence of zinc, which is said to weaken the joint by its presence 
in the alloy. 

Aside from these objections, a brazed joint is apt to be stronger 
than a weld, is generally cheaper, easier to make, takes less skill, 
apparatus, and time, and is often quite good enough for the 
purpose. 

Soldering. — A solder is a metallic glue. There are almost 
an infinite number of solders, the most common being lead-tin 
solder for soldering the common commercial metals. The lead- 
tin proportion is varied to obtain solders with different melting 
points, strength, fluidity, and elasticity. Then other metals 
are added to the original lead-tin alloy, so that the properties of 
the solder are given a different range. The solder may be used 
for special metals and special purposes. Either the lead or tin 
or both may be dropped. 

All solders have lower melting points than the metals they are 
intended to join; all solders must amalgamate with, or "wet," 
the metals they join. Most solders are weaker in tensile strength 
than the joined metals. For this reason soldered joints are not 
often intended to be specially strong. When metals are soldered 
in preference to being brazed or welded, it is because time and 
money can be saved and a satisfactory joint gotten. 

Ordinary solder is half-tin half-lead, by weight. Hard solder 
is two parts lead to one part tin. Hard solder is more brittle, 
stronger, and has a higher melting point. On account of 
the present high price of tin, it is also cheaper. To ordinary 
solder, antimony is added to still further harden and stiffen the 
solder. Arsenic is sometimes added to make the melted solder 
flow freely. Bismuth and cadmium are sometimes added to 
bring the melting point down. For example. Wood's metal con- 
tains two tin, two lead, two cadmium, and eight bismuth, and 
melts at 70 deg. Cent. Bismuth is apt to make a solder brittle; 
while cadmium, like tin, helps to make the solder elastic or soft. 
Copper in small proportion will stiffen and strengthen solder, 
but it will raise the melting point sharply. Iron is seldom used 
in solders. 

The data on the proportions of these metals in the solders is 
very inexact, and the exact properties of a given alloy are seldom 



BRAZING AND SOLDERING 171 

known. The whole subject comes under the study of alloys, in 
which there is still much confusion and little accurate informa- 
tion. New alloys are being put on the market every day, some 
of them of known constitution, some unknown; many of them 
have properties claimed which they do not possess, and the 
practical men must find out for themselves which of the solder 
alloys are fit for the purposes they are advertised for. The 
future will see more accurate information at the call of the metal 
worker, who will be able to choose his solder with an eye to get- 
ting certain properties in the alloy and at the lowest cost. 

The soldering hit is a copper-headed tool used to melt and 
manipulate the solder. The head is of various shapes, accord- 
ing to the work at hand, and is 

fairly bulky so that it will hold ^l I ^ ^^'^^^hZII _) 

heat for a period of time (see Fig. 

V -r, • 1 -1 1 Fig. gi. — Ordinary soldering; iron. 

91). It IS also pomtcd so as to be 

handy for working into seams and corners. The bit should 
be coated around the point with tin or the solder that is to be 
applied. This is so that when hot it will be coated with a skin 
of melted metal which will draw the solder with it. To tin the 
bit it is first filed or sand-papered free of scale, is fluxed with 
zinc chlorid, and then heated. It is then tinned by holding a 
tin stick against it and melting off some of the tin, which will 
adhere to the freshly fluxed surface. If the bit is at any time 
heated to redness while using, the tin will volatilize and the bit 
must be retinned. 

An ingenious soldering bit, or iron, recently patented, is de- 
scribed in the Brass World for February, 1905. The body of the 
bit contains a small reservoir in which is placed the solder. The 
reservoir has an opening near the head of the bit, which is opened 
by pressing a lever on the handle of the bit. The reservoir is so 
designed that the solder will not spill out while the workman 
is using it. 

Fluxes for ordinary plumbing soldering are sal ammoniac, 
borax, resin in alcohol, tallow, or zinc chlorid solution. There are 
a number of patent or secret fluxes on the market, and many 
metal workers make their own special preparations. The solder- 
ing flux is generally applied before heating and after the metals 



172 WELDING 

have been cleaned. Its office is to combine chemically with 
any oxid left after the mechanical cleaning and also to dissolve 
any grease. A well-fluxed surface is made of raw metal, ready 
to be wet by the solder. 

Sal ammoniac may be powdered on or applied with a brush 
as a solution in water. Calcined borax is powdered on or its 
solution painted on. Zinc chlorid is made by dissolving zinc to 
saturation in dilute hydrochloric acid. It is considered the best 
flux for plumbing. 

Some solders are known as self-Jiuxing. They contain a 
metal which oxidizes when heated or which is a solvent for the 
oxid on the surface to be soldered. For example, Richards' alum- 
inum solder is applied without flux. It contains phosphorus, 
which acts as a flux with oxid of aluminum. Self-fluxing solders 
should become popular in the future, when they are better 
known. 

Soldering commonly requires much less heat than welding or 
brazing. The solders have melting points one-half to one-fourth 

as high, and the joints do not need 
to be annealed or cooled slowly. 
Hence a mouth blowpipe with a 

Fig. 92. — Ordinary mouth blowpipe. n n ,t^- 

candle flame (rig. 92) or a foot 
pump with a gas flame will give all the heat needed. In solder- 
ing large joints, where the heat is conducted away rapidly by 
the body of the metal, a gasoline or kerosene torch is used for 
preheating, and the solder is melted in a tinner's soldering furnace. 
For soldering jewelry and filigree an ordinary blowpipe is used. 
No special precaution need be taken with the flame, except to 
keep it hot enough to consume ah of its carbon.. 

I will not try to describe any special soldering process. There 
are too many metals that can be soldered, and too many ways to 
solder them, and too many special solders for a given joint. In 
general, the process of soldering includes: the mechanical cleaning 
of the surfaces of the metals to be soldered; the heating to a point 
where the solder will unite with the clean surfaces; the fluxing of 
the surfaces, before or after heating, so that the metal surfaces 
will be really clean; the application of the solder with the bit; and 
the finishing of the joint. 



GRAZING AND SOLDERING 



173 



Blue Cone 
fOxydizing) 



Pale Red Flame 
(Reducing) 




In cleaning the metals, remove the rust and grease with a 
file, scraper, and a rag or alkali solution. If the flux is a liquid, it 
is best to first heat the metal a Httle and then paint on the liquid, 
which will eat away the oxid film, and will keep the clean surface 
covered until the solder is appHed. If the flux is borax or resin 
in solution, first apply cold. 

The solder is then melted on to the hot clean metal with a 
torch, or by pressing the hot bit against the solder stick and 
running it on to the metal. The 
bit is used to manipulate the solder 
over the surfaces and to give it the 
proper shape as it cools. 

Among the precautions neces- 
sary are to be sure the metals are 
clean wherever the solder is intended 
to bind. This can only be done by 
careful fluxing. Then the metals 
must be hot enough, but not too 
hot. If too hot, they will be liable 
to oxidize in spite of the flux, should the flux be prepared for a 
low temperature only. Also, if the metals are too hot, they will 
make the solder highly liquid. The bit must not be heated too 
strongly or the tinning will be driven off and the bit will then 
be no more capable of guiding and shaping the melted solder 
than would a stick of wood. 

Many soldering runs, such as are found in the manufacture of 
fruit cans, are now done by automatic machinery; the cleaning, 
fluxing, and soldering being done in an endless chain, and the 
machine turning out the finished soldered job in a tenth the time 
it would take by hand, and making a neater, evener job. The 
soldering is done by dipping the fluxed metal in a bath of molten 
solder. 

The following solders are used for lead, zinc, copper, brass, 
iron; and with the addition of cadmium or bismuth, for tin 
and britannia. 



Fig. 93. — How to hold the blow- 
pipe in a candle flame. 



174 



WELDING 
Melting Points of Lead-Tin Solders' 



Name 


Lead 


Tin 


Melting point 
deg. Cent. 


Tin 

Soft solder 

Medium 

Hard solder 

Lead 


I 

I 
I 

2 

I 


I 

2 

I 
I 


228 
171 
188 
227 
320 





For soldering gold, Gee^ gives a table of solders with melting 
points of 983 deg. to 1020 deg. Cent, composed of about i part 
copper to 2 to 5 parts silver, and a small addition of zinc. In 
making up gold solders, it is quite as important to know what 
metals should not be used. Because gold is very easily ruined by 
certain metals, lead, tin, arsenic, and antimony should not be 
used in solders. Antimony is specially injurious, and bismuth 
in very small proportion will rob gold of its properties. 

For silver the hardest solder is 4 parts silver to i part cop- 
per. A softer solder is 4 silver, i copper, and i zinc. About 
5 per cent, tin makes a quick-running solder. Arsenic in vary- 
ing amount is also added to soften the solder. 

For platinum the solder was commonly gold of ordinary 
purity, melted on with a strong blowpipe. Since the introduction 
of the oxy-hydrogen flame, platinum is seldom soldered and 
almost all joints are welds. 

Aluminum has been much experimented on recently (see 
page 21). There are a number of aluminum solders on the 
market. One of the best known, Richard's alloy, is composed 
of 22 tin, II zinc, i aluminum, i phosphor-tin. This is a 
self-fluxing alloy, due to the action of phosphorus on the alum- 
inum oxid. Aluminum solders are pronounced in general to be 
unsatisfactory, because aluminum is electropositive to all other 
metals, and electrolytic action of a destructive nature is apt to 
set in some time after the joint is made, especially if the joint 
is exposed to water. Tin is harmful to aluminum and should 
not be used in its solders. It is claimed that tin will permeate 
into the aluminum in time and make it rotten and brittle. 

^Brass World, Nov., 1905. 

-"The Goldsmith's Handbook," Geo. E. Gee, 1903. 



I 



GLOSSARY OF TERMS 1 75 

GLOSSARY OF TERMS 

Burnt Metal. — If iron or steel is heated to bright white, it will 
crystallize when cooled. This will make it brittle, and makes 
the wrongly called burnt iron. To prevent this brittleness the 
metal must be worked or hammered when cooling. Steel espe- 
cially is easily burnt because its carbon is apt to crystallize with 
the iron to form brittle alloys, above bright red heat. 

Chamfer. — To bevel the edge of a sheet or bar of iron so that 
it will be the proper shape for welding. 

Cold-short. — When a metal is brittle below incandescence. 
Generally caused by an impurity, as i per cent, of phosphorus 
in iron. Pure zinc is cold-short at about 260 deg. Cent.; alumi- 
num above 600 deg. Cent. The latter may be said to be hot- 
short, but not red-short. 

Critical Temperature. — Used to designate the temperature 
at which the metal itself or any important constituent begins to 
crystallize. The more sharply defined are the critical tempera- 
tures, the less weldable is the metal, as high-carbon steel. 

Ferrite. — The mineralogical name for pure iron, to distin- 
guish from martensite, cementite, etc., which are terms for the 
iron-carbon series. 

Flux. — Any substance, compound, or mixture used to clean 
the surface of the substances to be welded or soldered. The 
flux must be chemically or physically active toward the surface 
impurities, but not toward the substances to be joined. Sand is 
a flux for iron, as it forms a fusible silicate with the iron scale, but 
has no affinity for the iron. Zinc chlorid is a flux for lead, zinc, 
copper, etc., to be soldered, as it dissolves the surface oxids, 
leaving a clean surface. 

High-carbon Steel. — A general term for a hard, brittle steel. 
The carbon content is about o. 50 per cent, or more. 

Oxidizing Flame. — A flame is commonly caused by the 
chemical union of oxygen with another substance. If the flame 
has more oxygen supplied it than is needed for perfect combustion, 
the free oxygen in excess makes it an oxidizing flame — one that 
rusts or burns the metal. A flame may be oxidizing in one 
place and reducing in another. 



176 WELDING 

Red-short. — When a metal becomes brittle at a red heat, it is 
said to be red-short. Generally caused by an impurity, as i per 
cent, of sulphur in iron, or a minute quantity of bismuth in lead 
or gold. 

Reducing Flame. — A flame in which the fuel is in excess 
of the oxygen necessary for perfect combustion. The tendency 
of such a flame is to draw some oxygen from the burned parts of 
the metal. At all events it prevents burning within its radius. 

Spelter. — Now used in commerce as the name for pure zinc. 
Spelter is also the name for half-and-half brass used for brazing. 
The best way to use this term is not to use it at all. 

Swage. — A shaping tool, used in finishing a weld. 

Upset. — To enlarge the metal pieces at the place where they 
are to be welded. The enlargement at the welded joint is called 
the upset. 



INDEX. 



Acetone, 94 

storage, 95 
Acetylene, 75, 90 

dissolved, 94 

flame, 96 

generator, 91 

storage tanks, 96 

welding, loi 
vs. riveting, 106 
Air gas torch for brazing, 167 

hydrogen flame, using, 119 
process, 118 
torch, 117 
Alloy, aluminum, 21 

brazing, 166 

copper, 25 

gold, 18 

in brazing gold and silver, i6() 

nickel, 27 

platinum, 17 

Richard's, 174 

silver, 19 
. soldering, 170 

welding, 99 
Aluminothermics, 122 
Aluminum, 20 

in welding iron, 9, i r 

solders, 174 

welding, 23, 99 
Armature shaft, weld, 151 
Armor plate, annealing with Thomson 

welder, 70 
Arsenic steel, 11 
.\uto frame, welded, 109 

Bar, for top welding, 2 

melt, 97, 98 

welding to plate, bo 
Bauschinger, Prof., results of tests by, 13 
Bernardos arc-welder, ^^, 35, t,S 

process, cutting wrought-iron plate, 42 



"Betsy Ann," repair of, 147 
Bevels for strong weld, 100 
Bit, solder, 171 

Blow holes in thermit weld, 132 
Blowpipe, holding in flame, 173 

hydrogen air, 117 

mouth, 172 

oxy-hydrogen, 117 
Boiler repairs, 102 

welded, 102 
Boracic acid as flux, 165 
Borax as flux, 165 
Boxes, mold, for thermit work, 127 
Brass, welding, 99 
Brazing, 165 

Ferrofix process, 160 

practice, 167 

repeat, 169 

stock, 169 
Break-switch Thomson, 49 
Bronze, welding, 90 
Burner, oxy-hydrogen, 118 
Burnt iron, 143 

metal, 175 
Butt weld, 4, 100 

welding pipes, 129, 137, 140 

Can, plunger, 142 

Carbid-feed acetylene generator, 91, 92, 

93 
Carbon content of welding iron, 9 

Cast iron, 8 

iron, welding, 97 

welding, 66 
Castings, mending, 141 

repairing with oxy-acetylene flame, 
108 
Chain making, 2() 

welding, 30, 61 
Chamfering, 175 
Chemistry of o.xy-acetylene flame, 113 



177 



178 



INDEX, 



Chemistry of thermit reaction, 152 

Chrome steel, 11 

Clamps for welding vertical pipe, it,() 

Cleaning pieces for thermit weld, 17,2, 

Cleft weld, 4, 5 

Coal fire for welding, 2, 5 

Coke fire for welding, 2, 4 

Cold-shortness, 175 

Colors of heated metals, i 

Contact, imperfect, 6 

Cooling, slow, 9 

Copper, 25 

in welding iron, 1 1 

power and time required to weld, 58 

to iron, welding, 60 

welding, 25, 26, 56, 98 
"Corunna," repair on, 148 
Costs, cutting steel, 112 

oxy-acetylene welding, 1 1 2 

pipe welding, 140 

thermit rail welding, 146 
Crank case, broken, 106 
• case with welded arms, 107 
Crucible for thermit-welding, 125 
Crystallization point, 7 
Cylinder, welded, 105 

Davis acetylene generator, 91, 92, 93 
Davis-Bournonville Co., apparatus for 

producing oxygen, 86 
Detonating gas, 80, 116 

Electric resistance heater, 69 

welding, 28, S3, 59, 7° 
Electrolysis of water, 80 
Electrolytic gases, 83 
Electrum, 19 

Energy absorbed in electric welding, 55 
Engine bed, welded, roS 
Epurite, 74 



Flame, oxy-hydrogen, reducing, 176 

welding, 5, 113 
Flue welder, 64, 65 
Flux, 2, 3, 6, 175 
for aluminum, 22 
brass, 99 
cast iron, 98 
copper welding, 26 
Ferrofix brazing, 160 
soldering, 171 
in brazing, 165 
plate form, 158 
welding gold alloys, 18 
soldering, 165 
Fouche torch, 75, 76, 78 
Furnace for brazing, t68 

Gas, detonating, 80, 116 

flame for brazing, 166 
for welding, 5 

welding, loi 
Generator, acetylene, 91 

for electric welding, 44 
Girder cut by oxy-acetylene flame, no 
Gold, brazing, 169 

solders, 174 

welding, 18 
Graphite in welding iron, 9 

Hadf eld's steel, 10 
Hammering in welding, 4, 7 
Hazard-Flamand cell, 82 
Heat of thermit reaction, 154 

too high, 7 

welding, 3 
Heating metals, 57 
High-pressure oxy-acetylene torch, 77, 

78 
Hot-flame welding, 73 
Hydrogen air blowpipe, 117 



Ferrite, 175 

Ferrofix brazing process, 160 
Fires, welding, 4 
Flame-cutting, in 

gas, for brazing, 166 

oxidizing, 175 

oxy-acetylene, 96, 101 
-hydrogen, 115, 116, 118 



Impurities, effect, 8 
Iridio-platinum, welding, 17 
Iron, burnt, 143 

cast, 8 

welding, 07 

chain, 30 

for welded pipe, 29 

girder cut by oxy-acetylene flame, no 



INDEX. 



179 



Iron, malleable, i 

power and time required to weld, 57 

soldering, 171 

to copper, welding, 60 

weld, I 

welding, 2, 56, g8 

wrought, I, 7 

Joint, brazed, 169 

plumber's sleeve, 140 

thermit, 131 
Jump weld, 4, 6 

Kirkaldy and Son, results of tests by, 14 

La Grange-Hoho process, electric welrl- 

ing, 33, 34 
Latitte joint, 6, 158 

welding plate, 15S 
Lap weld, 4, 6 

welding lead sheets with air-hydrogen 
flame, i iq 
Lead-tin solders, melting-points, 174 
Linde process of making oxygen, 83 
Lining for thermit crucible, 1 27 
Liquid-air process of making oxygen, 

83 
Locomotive flue welder, 64, 65 
frame, thermit welding, 145 
Low-pressure torch for oxy-acetylene, 

77> 78, 79 

Manganese in welding iron, 10 
Melt bar, 97, 98 

welds, 1 01 
Melting-point of lead-tin solders, 174 
Metal, burnt, 175 

cutting with electric arc, 41 
with oxy-acetylene flame, 109 

heating, 57 
Mold boxes for thermit work, 127 

for pipe welding with thermit, 13S 
thermit work, 130 
welding vertical pipe, 139 

rail, 128 

safeguarding in thermit welding, 134 

sand for thermit work, 128 

thermit, 129 
Motor armature shaft, weld, 151 



Nickel, 27 

plate, 27 

steel, II, 27 

thermit, 136, 154 
Nitrogen in welding iron, 12 

Oil flame for welding, 5 
Osmium, welding, 17 
Overheating iron and steel, 3 
Oxone, 87 
furnace, 90 
oxygen generator, 89 
Oxy-acetylene blowpipe weld, 140 
-acetylene flame, 16, loi, 109, 114 
process, 73 

system, high-pressure, 100 
torch, 41 

welding, cost, 112 
-hydrogen blast, 16 
blowpipe, 117 
burner, 118 
flame, 116, r iS, i k) 
process, 115 
Oxygen apparatus using oxygenite, S6 
burner, 89 

constant pressure regulator, 81 
from chlorate, 86 
generating, 74 
generator, 88 
in cylinders, 84 
processes of making, 83 
storage, 83 
Oxygenite, 74, 85 

Phosphorus in welding iron, 10 
Pipe, butt welding, 129, 137, 140 

welding, 29, 138, 147 
Piping of steel ingots, preventing, 143 
Plate, welding to bar, 60 
Platinum, 15 

solder, 174 

welding, 17 
Plumber's sleeve joint, 140 
Plunger can, thermit, 142 
Poling, 143 
Potassium chlorate method of generating 

oxygen, 74 
Power required to weld copper, 58 

required to weld iron, 57 



i8o 



INDEX. 



Preheating, 5, 97, 98, 99, 133 
Puddling process, i 

Rail, electrically welded, 67 

molds, 128 

patterns, 127 

thermit-welded, 67 

welding, 66, 68, 123 
Reaction in thermit welding, 135 
Red-shortness, 10, 176 
Regulator, oxygen constant pressure, 81 
Repair, boiler, 102 

welding, 102 

with oxy-acetylene torch, 103 

work, thermit, 130 
Repeat brazing, 169 

welding, 43 
Richard's alloy, 174 
Riveting vs. acetylene welding, 106 
Roessler and Hasslacher Co., oxone 

oxygen generator, 89 
Royal Prussian Testing Institute, weld- 
ing tests, 13 

Sand, mold, for thermit work, 128 
Scarf, 2 

weld, 4 
Schuckert apparatus for electrolysis of 

water, 82 
Seal, safety water, 80 
Separation planes in thermit weld, 

132 
Setting pieces for thermit weld, 132 
Silicon in welding iron, 9 
Silver, 19 

brazing, 169 

solders, 174 
Smith welding, 2, 26, 31, 159 

welds, tests, 12 
Solder, 170, 173 

for aluminum, 21 
silver, 20 

hard, 19, 170 

self-fiuxing, 172 

soft, 19 
Soldering, 165, 170 

bit, 171 

fluxes, 165 

process, 172 



Spelter, 176 

for brazing, 166 
Sponge platinum, 16 . 
Steel, arsenic, 11 

chrome, 11 

compared with wrought iron, 2 

cost of cutting, 112 

high-carbon, 175 

nickel, 11 

silicon, welding properties, 10 

thermit, 121, 152 

welding, 7, 98 
Stock brazing, 169 

welding, 28, 30 
Storage, acetone, 95 

oxygen, 83 

tanks, acetylene, 96 
Sulphur in welding iron, 10 
Swage, 176 

Tank, welded, 103, 104 
Tap hole of thermit crucible, 126 
Tapping crucible, 130 
Temperature, critical, 7, 175 

of oxy-acetylene flame, 114 

range of weld iron, i 
Tests of acetylene welds, 115 

of electric welds, 70 
Lafitte welds, 159 
pieces treated with Ferrofix, 163 
smith welds, 12 
thermit welds, 155 

welding, 13 
Thermics of oxy-acetylene flame, 113 

of thermit reaction, 152 
Thermit, 8, 28, 147 

amount to use, 124, 131, 135 

commercial, 152 

crucible, 126 

in foundry practice, 142 

joint, 131 

mold, 129 

nickel, 136, 154 

plunger can, 142 

poling, 144 

process, 108, 121, 144 

repair work, 130 

titanium, 137 

to prevent piping of steel ingots, 143 



INDEX. 



l8l 



Thermit, welded rail, 67 

welding, practice, 131 

welds, tests, 155 
Thimble, 126 
Thomson automatic break switches, 40 

electric welder, 45, 46, 54 

machine for welding hubs and 
spokes, 51 

process, electric welding, ;^^, 42, 66, 68 

reactive coil, 48 

specimens, 61, 63, 64 

welders, 47, 50, 52, 53, 70 
Time required to weld copper, 58 

required to weld iron, 57 
Tinning soldering bit, 171 
Titanium thermit, 137 
Top welding, 2, 6 
Torch, air-hydrogen, 117 

for brazing or soldering, 166 

oxy-acetylene, 75 
Tubes, welded, 103 

Unwin, W. C, results of tests by, 14 
Upsetting, 4, 176 



Water, electrolysis, 80 

-feed acetylene generator, 92, 93 

-pail forge, 34 

seal, safety, 80 
Watertown Arsenal, tests of electric 

welds, 70 
Weld, diflferent kinds, 4, 6 

large, 8 

melt, 1 01 

poor, causes, 6 

smithed, 2, 6, 12 

thermit, 146 
Welding, electric, 28, ^3, 59> 7° 

hot-flame, 73 

smith, 2, 26, 31, 159 

with gas and acetylene, comparison, 

lOI 

oxy-acetylene flame, 97 
Weldite, 154 
Working, 4, 7 
Wrought iron pipes, 29 
iron, welding, 98 

Zerener electric blowpipe, 33, 34, 35 



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